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COMPRESSED AIR 

Its Production, Uses, and Applications 



COMPRISING 

THE PHYSICAL PROPERTIES OF AIR FROM A VACUUM 
TO ITS LIQUID STATE, ITS THERMODYNAMICS, 

COMPRESSION, TRANSMISSION AND USES 2j£$L 

MOTIVE POWER 

In the Operation of Stationary and Portable Machinery, in Mining, Air Tools, 
Air Lifts, Pumping of Water, Acids, and Oils; the Air Blast for Cleaning 
and Painting, the Sand Blast and its Work, and the Numerous 
Appliances in which Compressed Air is a Most Con- 
venient and Economical Transmitter of Power for 
Mechanical Work, Railway Propulsion, Re- 
frigeration and the Various Uses 
to which Compressed 

Air has been , 

Applied. 



WITH FORTY AIR TABLES AND FIVE HUNDRED AND FORTY-FIVE ILLUSTRATIONS 



By GARDNER D. HISCOX, M.E. 

Author of "Mechanical Movements, Powers, Devices and Appliances," 'Gas, Gasoline and 
Oil Engines," "Horseless Vehicles, Automobiles," etc., etc. 



NEW YORK 

NORMAN W. HENLEY & CO 
132 Nassau Street 



THE LIBRARY OF 

©ONGRESS, 
Two Copies Received 

NOV. 9 1901 

Copyright entry 
CLfcSS c*s XXc. No. 

copy a 



Copyright, igoi, 
By NORMAN W. HENLEY & CO. 



^ 



COMPOSITION AND PRINTING BY 
E PUBLISHERS' PRINTING COMPANY, 
NEW YORK, N. Y., 
U. S. A. 






PREFACE. 



THE literature on the commercial uses of compressed air, 
especially in its application to the mechanic arts, has not 
kept pace with the growing importance of the subject, having 
been confined, in the main, to occasional papers presented to 
engineering societies, and to special articles appearing at inter- 
vals in the various technical journals of this and foreign coun- 
tries, or in the still more fugitive~Torm of trade circulars; but 
even these, fragmentary publications at best, cover scarcely 
more than the past two decades. 

The thermodynamic treatment of air under compression, its 
transmission and expansion, have been ably worked out by care- 
ful experimenters and communicated to scientific societies by 
competent writers ; these articles, valuable in themselves, have 
not met the requirements of the modern engineer, whose imme- 
diate necessities demand a more complete gathering of the 
widely distributed data relating to this subject, as well as a better 
classification of the known properties of the atmosphere. This 
want has long been apparent to the author by reason of many 
years' experience in answering constantly -recurring inquiries 
relating to compressed air, and to its direct application to the 
commercial needs of the day. The fund of information ac- 
quired and carefully preserved by the author during the many 
years of his editorial work is now brought into compact form 
and in a single volume for ready reference. That this has been 
no light task will be apparent from even a casual perusal of the 
present work. 

The progressive advancement in experimental research ex- 



8 PREFACE. 

tends in two opposite directions: the partial vacuum incident to 
the ordinary operations of an air pump or the condensation of 
watery vapor has been extended by other methods to the 
highly attenuated results obtained in the manufacture of incan- 
descent lamps; while, on the other hand, compression has ex- 
tended through its various stages until, and in connection with 
a very low temperature, the final product, liquid air, has been 
made commercially available. Many of the difficulties in regard 
to the expression of mathematical details and thermodynamic 
formulas have arisen in consequence of this progressive ad- 
vancement; so also, the knowledge of the atmospheric relation 
to other elements is yet in a progressive state ; the practical ap- 
plication of compressed air for doing mechanical work is of so 
recent date that the design and construction of any of the most 
useful machines operated by compressed air rest upon empirical 
rather than scientific formulas. It is one of the objects of the 
present volume to make available the ascertained facts of ex- 
perimental research in atmospheric phenomena, and, so far as 
possible, the fundamental basis upon which such ascertained 
facts securely rest. 

To limit the consideration of the properties of air when sim- 
ply compressed above the ordinary pressure of the atmosphere 
was believed to be wanting in scope to make the treatment of 
the subject complete; this work includes, therefore, a consider- 
ation of the properties of air below atmospheric pressure, for 
the reason that we are surrounded by an atmosphere compressed 
by gravity, but it is used in the arts in many ways much below 
atmospheric pressure, even approaching the zero condition of a 
vacuum, so that, remote as the connection appears, this subject 
of partial pressures below the atmosphere properly belongs to 
a treatise on compressed air. 

The wide range of manufacturing interests in which com- 
pressed air plays an important or even a subordinate part is 
such that special machines for its production and utilization 
areas numerous as the diversified industries of our day; this 



PREFACE. 9 

condition has suggested the large number of illustrations em- 
ployed to place before the reader the salient features of only 
the latest and best designs. These designs include portable 
machines, together with a large number of individual and spe- 
cial tools designed for and greatly contributing to the lessening 
of manual labor, as well as tending to increase the output of 
useful work. 

The development of the caisson method in submarine work 
for engineering structures has become very general; requiring 
not only special appliances, but introducing problems in hygiene 
which do not ordinarily occur in engineering practice ; the sen- 
sations and physical effect of varying air pressures and temper- 
atures upon workmen engaged in labor of this kind belong es- 
sentially to the subject-matter of this work, and have been 
included. 

Within the past few years an important and useful com- 
mercial effect has been obtained by the use of compressed air 
and its subsequent expansion in the production of temperatures 
suited to refrigerating purposes ; such machines are in use on 
warships and other vessels in which, for one reason or another, 
the use of ammonia gas is either objectionable or prohibitive. 

The author, recognizing the economic value of such ma- 
chines, has given considerable space to the consideration of the 
physical and thermodynamic problems connected therewith. 
There are many interesting problems in this connection which 
lie beyond the domain of commercial refrigeration, in which, 
by the production of temperatures far below the Fahrenheit 
zero and approaching the absolute zero, the critical temperature 
of air is passed and its physical condition changed from a gase- 
ous to a liquid, and thence to a solid state; as this subject has 
been fully treated in a recent volume on Liquid Air, it has 
therefore been given but limited space in this work. 

Among the available sources of information employed by the 
writer have been the various standard treatises on thermody- 
namics, including Weisbach, Rankine, Roentgen and Dubois, 



IO PREFACE. 

Thurston, De Volson, Wood, and others ; free use has been made 
of articles on compressed air and its appliances which have ap- 
peared in the Scientific American from time to time ; acknowledg- 
ment is also due to the leading technical journals of this 
country and of Europe ; while the writer would be wanting in 
appreciation and gratitude if he failed to suitably acknowledge 
the action of his friend Mr. William L. Saunders, editor and 
proprietor of the journal Compressed Air, who, with charac- 
teristic liberality, tendered the entire valuable contents and 
illustrations of this journal to the use of the author in the prep- 
aration of this volume. Gardner D. Hiscox. 

New York, November, iqoi. 



CONTENTS. 



CHAPTER I. p AGE 

Historical, 13 

CHAPTER II. 
Physical Properties of Air 29 

CHAPTER III. 
Air in Motion and its Force, . .41 

CHAPTER IV. 
Air Pressures Below Atmospheric Pressure, 49 

CHAPTER V. 
The Flow of Air under Pressure from Orifices into the Atmosphere, 89 

CHAPTER VI. 
The Power of the Wind, 97 

CHAPTER VII. 
Isothermal Compression and Expansion of Air . . 113 

CHAPTER VIII. 
Thermodynamics, . . .119 

CHAPTER IX. 

Adiabatic Compression and Expansion, . . . ... . . . 133 

CHAPTER X. 
The Compressed-Air Indicator Card, 153 

CHAPTER XI. 
Actual Work of the Compressor, 163 

CHAPTER XII. 
Multi-Stage Air Compression, 175 

CHAPTER XIII. 
The Expansion of Compressed Air and the Work of the Motor, . 195 

CHAPTER XIV. 
Transmission of Power by Compressed Air, 211 

CHAPTER XV. 
Compressed Air Reheating and its Work, . . . . . . . 223 

CHAPTER XVI. 
The Compressed-Air Motor, . 241 



Xll CONTENTS. 

CHAPTER XVII. page 

Efficiency of Air Compressors at High Altitudes, . . . . 255 

CHAPTER XVIII. 
Air Compressors (Descriptive) , 269 

CHAPTER XIX. 
Air Compressors — Continued, 291 

CHAPTER XX. 
Air Compressors — Continued 337 

CHAPTER XXI. 
Air Compressors — Continued, 367 

CHAPTER XXII. 
Compressed Air in Mining and Quarrying, . . 415 

CHAPTER XXIII. 

Pneumatic Tools — The Pneumatic Hammer and its Work, . . . ^45 

CHAPTER XXIV. 
Pneumatic Tools — Continued, 497 

CHAPTER XXV. 
Air as Applied to Pyrometry, 553 

CHAPTER XXVI. 
Compressed Air -in Railway Service, 571 

CHAPTER XXVII. 
Pneumatic Work, 611 

CHAPTER XXVIII. 
Pneumatic Work — Continued 627 

CHAPTER XXIX. 
Pneumatic Work — Continued, 661 

CHAPTER XXX. 
The Pneumatic System of Tube Transmission, 673 

CHAPTER XXXI. 
Compressed Air in Warfare 693 

CHAPTER XXXII. 
Compressed Air Work, 709 

CHAPTER XXXIII. 
Refrigeration, 745 

CHAPTER XXXIV. 
The Hygiene of Compressed Air, ....... -773 

CHAPTER XXXV. 

Liquid Air, its Properties and Uses, 785 

CHAPTER XXXVI. 
List of Patents from 1875 to July, 1901, 803 



Chapter I. 



HISTORICAL 



HISTORICAL. 

The use of air in its lower condition of compression for 
power and for mechanical purposes has been known from the 
earliest ages, and antedates any knowledge we possess of the 
use of steam by many generations. 

The reduction of metals from their ores and the forging of 
iron and steel brought the forge and the blast furnace, with the 
use of air under pressure, into existence as mechanical appli- 
ances more than two thousand years before the Christian Era. 

The evidences of the use of the air blast under compression 
are plainly seen depicted on the sculptured walls of the 
structures of the oldest civilization, and are made still more 
manifest in its endurated paintings and in the legends of the 
early historians. 

The first inception of air power, as gathered from the 
example of the winds, seems to have been less progressive in 
its uses than other of the mechanical arts ; for, while it formed 
one of the vital elements in producing the metals, the inventive 
instinct in handicraft seems also to have been instilled in the 
early workers of metals in creating the tools that by the 
ancient genius of art worked out the models of beauty that are 
our examples of to-day. 

The old methods of compressed-air production seem to 
have taken on a crude and nearly stationary form for at least 
two thousand years before, and for more than a thousand years 
after, the Christian Era, and in some parts of the world may be 
seen in operation to this day. 

In China, India, Burmah, Borneo, Africa, and Madagascar 
the primitive methods of compressing air are still in use : the 



16 COMPRESSED AIR AND ITS APPLICATIONS. 

air treading- bags, the wooden cylinder and piston, and the 
Chinese wind-box are the common devices for producing the 
air blast. 

The only further progress that appears on record in regard 
to the production of compressed air and its uses for power 
purposes has been handed down in fragmentary history, and 
mostly contained in the pneumatics of Heron of Alexandria. 

From the descriptions extant, he seems to have been the 
first to invent or to describe the pressure air pump or 
compressor for pressures greater than the forge blast, and to 
have applied it in the famous fountain attributed to him. 
Notwithstanding the alleged ignorance of the ancients respect- 
ing the physical properties of the atmosphere, there are 
circumstances related in history which seem to indicate the 
reverse ; for Diogenes of Apollonia reasoned on its condensa- 
tion and rarefaction. 

The description of the fire engine of the Egyptians, as 
given in Heron's " Spiritalia," shows very plainly that the use 
of air compression and its elasticity in the air chamber of a 
hydraulic pump were well understood in the second century be- 
fore the Christian Era. 

The devices of the Egyptian priesthood for exciting the 
wonder and awe of the people, possessed as they were of the 
superstitions and proclivities of that age, were no doubt derived 
from a general knowledge of many of the physical laws of the 
elements possessed by the ruling and priestly classes. 

They understood the nature of the expansion and contrac- 
tion of air by heat and cold, of which the vocal statue on the 
plain of Thebes was an example. 

Tha movement of the statue of Serapis and the altar tricks 
of the Pharaonic priesthood are other examples of the designed 
antics, due to the use of compressed air and the vapor of 
water. 

Had it not been for the written work of Heron, the "Spir- 
italia," we should never have suspected that air was made to 



HISTORICAL. 17 

perform so important a part in ancient frauds, nor that its 
compression and expansion had been employed to raise 
liquids. 

Notwithstanding the high opinion which history gives us of 
the historical and philosophical knowledge of the old Egyptian 
priesthood, we should hardly have surmised that they had the 
art of applying this subtle fluid so ingeniously. They seem, 
however, to have searched all nature for devices ; and to have 
become familiar with many of the principles upon which the 
most valuable of our arts and mechanics are based. 

The condensing air pump or compressor must have been 
used in charging the wind guns of Ctesibius of Alexandria, 
about 120 B.C., as described by Vitruvius. The properties 
exhibited by a partial vacuum must have been well known from 
five hundred to one thousand years before the Christian Era, as 
illustrated in the use of the siphon and the atmospheric water- 
ing-pots of the early Egyptians, though the principle of the 
perfect vacuum is undoubtedly due to Torricelli, by his produc- 
tion of the mercurial vacuum, about 1643 a.d. 

The air-pressure bellows, in its many forms, seems to have 
been confined to a stated use, that of forcing a fire, from the 
earliest times, when a slight advance was made in air pressure 
to operate the devices and toys used in priestly incantations, 
followed by its application in the propulsion of projectiles by 
Ctesibius. 

Then its principles slumbered in its low-pressure use for 
more than a thousand years, when the arrow discharged under 
air pressure by Ctesibius finally developed into the pneumatic 
gun of Marin in France, which was presented to Henry IV. in 
1600. A more perfect compressed-air gun was brought out by 
Guter at Nuremberg in 1656, which had attached to the stock, 
in musket form, all the appliances for charging and discharging 
by air compression. But little further progress was made in 
this line until near the middle of the nineteenth century, when 
compressed-air guns took a wide range of design; their most 



18 COMPRESSED AIR AND ITS APPLICATIONS. 

useful and effective outcome being the pneumatic guns of 
Zalinski and others. 

While the mechanic arts slumbered through the dark ages 
in Europe, the Chinese seem to have improved the aboriginal 
piston blower by a more perfect action and finish, in an instru- 
ment styled by them the "wind-box." 

The water trombe, or tromp, for compressing air by a fall 
of water in a tube, used for blowing forges and other purposes, 
was known to Heron, and was mentioned by Pliny in his 
"Natural History." 

In improved form the tromp has held its place for two 
thousand years, and is in use at the present day in Europe and 
the Orient. 

The principle of Heron's pneumatic fountain for raising 
water was carried out on a large and useful scale in the pneu- 
matic pumping engine at the mines of Chemnitz, in Hungary, 
erected by M. Hoell in 1755; there was probably first illus- 
trated the refrigerating power of air when expanded from great 
pressure. In the lower chamber of this apparatus the discharge 
of air and its expansion with water produced hail or pellets 
of ice. At first this machine required personal attention in its 
manipulation, but in 1796 it was made automatic. 

The use of compressed air for submarine work was no doubt 
well known in the earliest ages, being almost coeval with the 
dawn of commerce. 

Aristotle (350 B.C.) describes a kettle in which divers sup- 
plied themselves with fresh air under water. The legend of 
the descension of Alexander the Great to the bottom of the sea 
in a vessel called a colympia, with a glass window in it, is no 
doubt an allusion to the use of the diving-bell. It was em- 
ployed in Phoenicia in the year 320 B.C., and the use of glass 
was well known then. 

Nothing further appears on record in regard to submarine 
work with a bell for more than fifteen hundred years, when 
mention of its use in Spain in 1538 is met with. Bacon de- 



HISTORICAL. 19 

scribes it (1620) as a machine used to assist persons laboring 
under water upon wrecks, affording a reservoir of air into which 
they could enter to take breath. 

From this time on for a hundred years the diving-bell was 
largely used in Europe in recovering wreckage and treasure; 
in 171 5 Dr. Halley made the first contrivance for supplying 
the diving-bell with fresh air by lowering air-filled barrels and 
discharging the air under the bell, letting out the foul air at 
the top through a cock; or of allowing of completely filling 
the space with air that was made unavailable heretofore by the 
compression of the air in the bell. 

Dr. Halley suggested the present system of submarine 
armor by using a cap or portable helmet connected with a 
tube leading to the surface, through which fresh air was forced 
to the helmet for the needs of the diver. Smeaton and Brunei, 
from 1779 on, improved on the use of the diving-bell, making 
its operation continuous by a fresh supply of compressed air 
through tubes from pumps. 

The submarine armor continued to be improved along the 
lines of its present form for deep-sea work, in which depths of 
148 feet have been attained, involving work under an air 
pressure of 65 pounds per square inch for several hours. It 
has been claimed that a depth of 200 feet has been reached 
without serious results from the great pressure due to that 
depth. 

The compressed-air and vacuum pump was greatly im- 
proved by Otto Van Guericke about 1650, and it has been 
claimed as his invention. 

Savary increased the pressure of air for blast furnaces by 
the use of more substantial blowers, in the latter part of the 
seventeenth century. 

Denys Papin was the first to propose and make, in 1653, 
an actual trial of the transmission of power to a distance by 
compressed air. His early ideas being finally developed into 
more practicable shape, they resulted in his recommending the 



20 COMPRESSED AIR AND ITS APPLICATIONS. 

use of water power for compressing air and forcing it to a 
distance for useful work, thus foreshadowing the now common 
practice of the long transmission and distribution of air through 
mines for the operation of machinery. 

His system of an air pump driven by a water wheel, oper- 
ating on air and water chambers at a distance, was in the right 
direction, but failed in its practical operation by the elasticity 
of the air, which he had intended to use as a long piston in 
transmitting power from an air-working piston to a distant 
water piston. 

It was the fertile and mechanical brain of Papin that first con- 
ceived the idea of the pneumatic tube for transmitting parcels by 
air pressure, thus antedating by more than two hundred years 
our pneumatic-tube postal and package service, and thus early 
opening the way for future advancement in the use of com- 
pressed air. 

Experiments were made in Wales in these early years to 
utilize water power for compressing air and transmitting it 
long distances for operating blast furnaces. 

In 1757, Wilkinson, in England, patented a method of com- 
pressing air by the use of a column of water, effecting his 
object by means of a series of chambers or water compressors, 
used one after another, so as to keep up a regular pressure ; 
thus, in a crude way, preceding by a hundred years the water 
compressor of Sommeiller at the Mont Cenis tunnel. 

Many vague descriptions of apparatus for the use of com- 
pressed air in the mechanic arts and for its compression are 
found in the English patents during the eighteenth century; 
but either their practical applications were never realized or 
else no record was made of their operation. 

The application of compressed air to practical uses and its 
transmission for power purposes seem to have commenced an 
era of advancement in the last years of the eighteenth century. 

Professor St. Clair, of the Edinburgh University, in 1785, 
proposed attaching air bags to sunken vessels beneath the 



HISTORICAL. 2 I 

surface of the water and inflating them by air pumps ; fol- 
lowed by its practical use for raising vessels, for which many 
patents have been issued in Europe and the United States for 
various modifications of this device. Its most successful trials 
were made in 1864 in raising a steamer sunk in Lake Boden, 
and in raising the vessels sunk at Sebastopol during the 
Crimean War. 

From that time on many patents have been issued for vari- 
ous devices for raising vessels by inflating floats by air pressure, 
and for compressing air and its use in diving-bells and sub- 
marine armor. 

Medhurst, a Danish engineer in England, in 1799 com- 
pressed air to 15 atmospheres (210 pounds), stored and trans- 
mitted it to a motor in a mine ; he patented a pneumatic system 
for conveying persons and parcels in tubes in 18 10, followed by 
publications during a period of several years on tubular trans- 
mission by compressed air. There is no record of the practical 
working of the many schemes of this fertile genius. 

Compressed air for driving vehicles seems to have had its 
birth with the beginning of the nineteenth century in a patent 
to Medhurst, in England, August 2, 1800, for means for propel- 
ling carriages by compressed air from a reservoir. 

Compressed air for tramway cars appears to have received 
an impulse in Wright's English patent, April, 1828; he also 
proposed the use of iron cylinders beneath the cars, with an 
additional cylinder for heating the air by a small furnace, to 
increase its expansive force before entering the working cylin- 
der and to mingle steam generated by the same furnace with 
the hot air. 

The air brake seems to have first taken shape at this time in 
Wright's patent with an eccentric on a wheel shaft, connected 
with a piston, which was to be operated as a brake on down- 
grades by pumping air into the air chambers; but it was not 
until 1 869 that air brakes began to take a practical form under 
the patents of Westinghouse. 



22 COMPRESSED AIR AND ITS APPLICATIONS. 

In 1828, Bompass, in England, patented and built a com- 
pressed-air locomotive. 

Parsey, in 1847, built and ran a vehicle in which an inter- 
mediate reservoir was provided for reducing and equalizing the 
air pressure to the cylinders. Baron von Rathlen built and 
ran a vehicle with compressed air in England in 1848, attaining 
a speed of 12 miles per hour on the best roads of that day; he 
also suggested an increased pressure to 750 pounds per square 
inch as desirable for road and locomotive power, and advised 
compound compression and intercooling. 

The earliest known appliance for making ice by the expan- 
sion of compressed air was invented and put into actual practice 
by Dr. John Gorrie, of New Orleans, La., in 1850, to whom a 
patent was issued in 185 1. The system of cold-room storage 
by the expansion of compressed air has since been greatly 
enlarged on the lines originated by Dr. Gorrie, and is in use 
in the meat and fruit transport service. 

Vallance again agitated the subject of tube transmission in 
England, in 18 18 and on, and proposed a cast-iron tube system 
for passengers and parcels ; followed by others with feeble ef- 
forts to establish the pneumatic tube system from about 1824; 
and again by William Mann with English patents in 1824. 

It was not until about 1865 that practical success was achieved 
by the Parcel Dispatch Company of London ; since then the 
use of this system for parcel and postal transmission has been 
greatly developed in Europe and in the United States. 

The first compound compression of air was probably sug- 
gested in the patent to William Mann in 1829, for what was 
then called stage pumping, — i.e. , the use of two or more cylin- 
ders with intercooling; which was then properly claimed not 
Only to effect great economy in compressing air, but also to de- 
crease the machinery strain and to admit of lighter construc- 
tion of the compressor. 

In 1830 and on, Clegg and Pinkus, in England, agitated the 
system of a slotted tube and travelling piston with a vacuum or 



HISTORICAL. 23 

air pressure, with connections to an outside carriage. Experi- 
ments were carried on through several years without success, 
although trials were made with short lines of slotted air tubes 
in England and Ireland. 

In 1830, Thilorier compressed gases to high pressures in 
stages, for which he received a medal from the French 
Academy. 

The air-plunger pump for producing fire by compressed 
air was a family adjunct before friction matches came into use, 
in the home of the writer's father, who, in 1833, employed an 
apparatus made by himself, consisting of a cast-iron barrel 
weighing several pounds, with a bore three-eighths of an inch 
in diameter, like a cannon without the vent. A steel piston, 
about eight inches long, was accurately and tightly fitted, but 
moved rather easily when lubricated. The end of the piston 
had a small cavity for receiving a piece of punk ; the handle was 
provided with a stop or shoulder to prevent the plunger from 
striking the bottom in its sudden movement. The weight of 
the barrel, pushed by hand, acted by its momentum to complete 
the final pressure of, probably, eight hundred or more pounds 
per square inch, with an instantaneous evolution of temperature 
to a red heat, which fired the punk. A quick withdrawal of 
the plunger and the touch of a sulphur match completed the 
operation of generating a fire. 

Following the agitation of the slotted-tube system of Clegg 
and Pinkus, in 1830, the subject was revived by Count Fon- 
tainemoreau, in 1844, and trials were made with unsatisfactory 
results. 

The parcel-tube transmission system was again brought to 
the surface in England about i860. A thirty-inch tube, a 
quarter of a mile in length, was constructed at Battersea, and 
afterward removed to London and used for conveying the mail 
between district offices. 

This was followed in 1864 by a larger and longer line in 
London. 



24 COMPRESSED AIR AND ITS APPLICATIONS. 

The trials of Mr. A. E. Beach in New York, in 1867, with 
an eight-foot subway under Broadway for the propulsion of 
passenger cars by air pressure, seemed a step in the right di- 
rection, and failed only from apathy in financial circles. 

The pneumatic-tube system simply slumbered for a time, 
and was then developed into its most useful work; at the pres- 
ent time it is largely in use for interpostal and telegraphic-office 
connections throughout Europe and the United States. The 
store cash system, in its intricate detail, promptness, and ac- 
curacy, is a modern wonder. 

Compressed air for machine-driving, crane-hoisting, and 
other mechanical purposes was agitated in England in 1840 and 
on, with patents on detail plants for the transmission of com- 
pressed air from a central station to distant hoisting engines in 
warehouses and on docks. Ericsson, in 1858, compressed air 
by the power of caloric engines, for operating hoisting-engines 
in warehouses in New York, followed by a practical system for 
running sewing-machines in large numbers from a central 
station by the transmission of compressed air to small motors 
on the machines. 

Compressed air for high working pressures, generated by 
hydraulic pressure and the use of waterfalls, was an improve- 
ment on the antiquated methods by the use of the trompe. 

The direct pressure system was brought into use by Som- 
meiller at the Mont Cenis tunnel in 1872, and did good work at 
that time ; but as it required as much water to compress the air 
as was equal to the amount of free air compressed, the system 
was applicable only in favorable localities, and has now 
dropped out of use. Many patents have since been issued on 
direct-acting hydraulic air compressors, but the principle is not 
economical in practice, and we know of no compressors of this 
class in use at the present time. 

The trompe system has been greatly improved and extended 
for high pressure, with a large flow of water with moderate 
head, by making a deep pit with an air chamber at the bottom 



HISTORICAL. 25 

and returning the water to the foot-fall as in an inverted 
siphon. This was first demonstrated in experiments by Mr. J. 
P. Fizell, of Boston, in 1877, and patented in 1878. It has been 
finally put in practical operation by Mr. C. H. Taylor in large 
instalments of hydraulic plants at Magog, near Montreal, and 
at Ainsworth, British Columbia. 

Both plants have proved a success, and the utilization of 
water power for compression of air and its transmission for all 
power purposes is thereby assured. 

The vertical excavated shafts may not be needed where 
steep slopes, or chasms, or mountain sides are available. The 
moving water will carry air down a slope as well as by vertical 
shaft, and the return pipe only follows the same line back, so 
that the friction due to the additional length of flow line is the 
only loss in effiicency. 

Compressed air for street railways was continually agitated 
by newspapers and promoters during the middle of the nine- 
teenth century. But little practical progress was made, much 
of the difficulties and obstructions being due probably to the 
distrust of the moneyed interest of schemes that had no practical 
and reliable tests and trials. 

In 1862 the writer made plans for a light car street-railway 
system with compressed-air storage under the seats and on top 
of the car, with the engine under the platform, so that the 
passenger accommodation was not interfered with. The air 
pressure of two hundred and fifty pounds was to be supplied 
from station storage tanks and a compressor on the line. The 
plans did not meet with financial encouragement, and proved 
to be premature. The horse was not yet ready to go. Another 
generation was needed to bring compressed-air power for rail- 
ways to a financial acceptance. 

Further progress was made about 1873 in the intercooling 
of the compressing air in the cylinders by water jets or sprays, 
in the compressors at the St. Gothard tunnel. This led to still 
further improvements and economics in the construction of air- 



26 COMPRESSED AIR AND ITS APPLICATIONS. 

compressing machines; until at the present day there seems to 
be nothing but change of detail in construction — that may not 
always result in improvement. 

The introduction of compressed-air-hauling locomotives in 
the St. Gothard tunnel was a successful turn in favor of com- 
pressed air for railway work, and seemed to stimulate efforts 
in that direction; it was soon followed by the Mekarski and 
Beaumont compressed-air railway systems in Europe, with 
increased air pressure and better appliances for economical 
compression and motor use. Compressed-air locomotives for 
mine haulage continued to improve in constructive details, and 
are now largely in use in the United States. For mining pur- 
poses compressed-air appliances have been steadily perfected, 
until at the present day there seems to be little room left for 
greater improvement except changes in detail, if such can be 
really called improvement. 

The use of compressed-air machinery for quarrying, min- 
ing, and tunnelling, and the means of compressing air along 
economical lines, have been greatly extended by the inventive 
genius of Burleigh, Ingersoll, Sergeant, Rand, Clayton, and 
others, who have contributed to and promoted the economy of 
practical operation in rock-boring machinery that has so greatly 
aided in excavating the vast system of railway tunnels of the 
United States, and in sinking and drifting in the mines of all 
countries during the past quarter of a century. 

Every implement required in the generation of compressed- 
air power and its uses has overflowed its earlier and narrow 
field of work, and is now encompassing a wide area of useful- 
ness in our workshops, factories, and in hundreds of industrial 
operations: transportation, railway appliances, refrigeration — • 
even unto the painting of buildings and structural work, and 
the dusting of furniture, carpets, and clothing. 

The later development and actual application of compressed 
air at extremely high pressures, and its economical use by 
reheating, derived from the persistent efforts of Mekarski, 



HISTORICAL. . 27 

Beaumont, and others in Europe, and of Judson, Hoadley, 
Knight, and Hardie in the United States, have brought the use 
of compressed air to a new condition of application, and a high- 
pressure storage of 2,500 or more pounds per square inch in a 
condensed space of from 170 to 180 volumes in one volume. 
This allows for sufficient storage volume within the limit of 
passenger-car and vehicle capacity for runs of reasonable 
distances. 

The precise limit of the compressibility of air at ordinary 
temperatures is as yet an unknown quantity. It has been com- 
pressed to 14,000 pounds per square inch in experiments for 
blasting rock ; and it has been asserted, and there seems to 
be no reason to doubt, that any pressure may be obtained 
within the limit of safety in the strength of metals to hold the 
pressure. 

The assertion has been made by experimenters with high 
air pressures that 20,000 or more pounds per square inch may 
be made available for special purposes ; this is far below the 
explosive power of gunpowder. 

The blasting effect of air at high pressure in coal mines 
was noted in a series of trials at Denton and Wigan, England, 
in 1877-79. 

During these trials a pressure of 14,200 pounds per square 
inch was attained by the comparatively crude methods of those 
days. As compared with powder, the trials were successful in 
the saving of time and in the health and safety of the men ; 
but the cost of production exceeded that of explosives, and the 
scheme was abandoned. 

The experiments in high air pressures conducted by Mr. 
Perkins, a noted engineer, in England, and detailed in a paper 
read to the Royal Society, June 15, 1826, are most interesting, 
as demonstrating the liquefaction of air at ordinary temperature. 

Mr. Perkins used a cast-steel pump, tested to 2,000 atmos- 
pheres, nearly 30,000 pounds per square inch, with water. 
Using the same pump for air, he observed the then curious 



28 COMPRESSED AIR AND ITS APPLICATIONS. 

phenomena that induced him to carry the compression of air to 
the highest limit possible. 

At 500 atmospheres, nearly 7,500 pounds, the air began to 
disappear, apparently by partial liquefaction ; at 800 atmos- 
pheres, still further liquefaction was observed; at 1,000 atmos- 
pheres, 14,700 pounds, small globules of liquid air formed in 
the tube; and at 1,200 atmospheres, 17,640 pounds per square 
inch, a beautiful transparent liquid was seen in the glass 
compression tube. 

Few attempts were made to liquefy air for many years suc- 
ceeding Perkins' experiments, until about 1877, when Raoul 
Pictet, Cailletet, Dewar, Olzewski, and others followed in the 
line of producing liquid air by the cold or low-temperature 
process and moderate-compression system. 

Michael Faraday had been experimenting on the liquefac- 
tion of air and other gases since 1823 with indifferent results. 
More recently Professor Linde, in Germany, has by improved 
and larger appliances liquefied air in large quantities. 

Tripler and others in the United States have made liquid 
air a commercial commodity. 

Its practicability as a motive power has been doubtingly 
questioned, and even ridiculed ; but the fact is in evidence that 
it has the qualifications of a power mover, and can be controlled 
for any required pressure. Its practicability and economy are 
now being tested ; as a refrigerant, its power is amazing. 

The number of United States patents for compressed-air 
devices and appliances has gradually increased during the past 
century, and is now upward of four thousand. 



Chapter II. 



THE 

PHYSICAL PROPERTIES 

OF AIR 



THE PHYSICAL PROPERTIES OF AIR. 

Air as it exists at and near the surface of the earth is a 
mechanical compound or mixture of several gases, principally 
nitrogen, filling 79 parts by volume, or yy parts by weight, 
and oxygen, approximately 21 parts by volume, or 23 parts by 
weight. The relative volumes of nitrogen vary to an amount 
of about five per cent in different localities. 

In air expelled from water by heating, Bunsen found 34.9 
parts by volume of oxygen and 65. 1 parts by volume of nitrogen. 
This change, made by contact with water, in the constituent 
volumes of air may be partly accounted for by the absorption 
of the carbonic acid gas and the formation of ammonia from the 
nitrogen of the air and hydrogen from the water, which would 
liberate oxygen. 

This singular change in the constituents of air, when 
absorbed by water, may have an important bearing upon the 
existence of marine life that we have not yet seen discussed. 

A minute percentage of from .002 to .005 of carbonic acid 
gas, a lesser amount of ammonia, and the newly discovered 
argon, amounting to about one per cent, in volume, are always 
present in air. The vapor of water is ever present in the 
atmosphere at seldom less than 50 per cent of saturation, at 
which point it holds .00044 of a pound of water per cubic foot 
of air at 62 F. ; and at the point of saturation and temperature 
of 62 F. it holds .00088 of a pound per cubic foot of air. 

The expression of "dry air," used by our air-compressor 
friends, is only relative, and air can only be considered dry when 
the amount of moisture is at less than 50 per cent of saturation 
for any given temperature ; the amount of moisture actually 
varies with the temperature to three times less at 32 ° F. to 
three times more than the above figures at 92 ° F. 



32 COMPRESSED AIR AND ITS APPLICATIONS. 

Air is absorbed by water in a decreasing ratio from 32 F. 
upward to a temperature at which vapor becomes visible and at 
atmospheric temperature. Increased absorption of air by water 
takes place under increasing pressure; hence, the frequent loss 
of air in the air chambers of pumping-machines and water rams. 

TABLE I. — Comparative Volume of Air Absorbed by Water at Various 
Temperatures, in Volumes. 



32" F 0.02471 

41 02179 

50 01953 

59 01795 



68° F 0.01704 

77 01632 

86 01556 



To the loss of air in free running water at the higher tem- 
peratures in the table is probably due the insipidity of such 
water as compared with its taste between the temperatures of 
32 and 41 F. 

The weight of absolutely dry air at the sea level in middle 
latitudes and mean barometric pressure of 29.92 inches and at 
32 F., is .080728 pounds per cubic foot; at 62 F. it weighs 
.0761 pounds per cubic foot, and is 819.5 times lighter than 
water, which weighs 62.355 pounds per cubic foot at the same 
temperature, viz., 62 ° F. 

Air at the barometric pressure of 29.92 inches, 14.7 pounds 
per square inch, or 2166.8 pounds per square foot, and at the 
temperature of 62 F., requires 13.141 cubic feet to equal 1 
pound avoirdupois ; and in ordinary computation these figures 
are used for the normal conditions of the atmosphere at sea 
level in mid-latitudes. 

If its whole volume were of equal density with the above 
pressure (14.7) at sea level, its limit of height would be -.VVIt' 
equal to 27,816 feet, a quantity used in computing for atmos- 
pheric head (h) in the formulas for the flow of air through 
orifices at a mean temperature of 62 ° F. 

The height of the atmosphere appears to have no determinate 
limit, but it gradually fades away in density and pressure to its 
confines with interplanetary space. At about forty miles the 



THE PHYSICAL PROPERTIES OF AIR. 33 

refractive effect of twilight ceases; above that elevation the air 
is either too rare or too pure from foreign particles to send us 
any perceptible reflection or illumination. 

There is abundant evidence, however, from the phenomena 
of meteors that the atmosphere extends to a height of one 
hundred miles at least, and it cannot be asserted positively that 
it has any well-defined upper limit. 

By virtue of the expansive force of the air, it might be 
supposed that the air in the upper atmosphere would expand 
indefinitely into the planetary space. But there are opposing 
forces that seem to limit its expansion. In proportion as the 
air expands in the upper regions of the atmosphere its expan- 
sive force is weakened and decreased by loss of heat, which 
partially counteracts its expansion, and with gravity probably 
holds its limit near the zone of absolute zero of temperature. 

Below the level of the sea, as in the valley of the Dead Sea 
and in the shafts and adits of deep mines, the density of the 
atmosphere increases in the same ratio as above the sea level 
for equal temperatures and humidity. Such depths are indi- 
cated by the barometer under the same conditions as for the 
upper atmosphere. 

The atmosphere obeys the law of compression and expansion 
when kept at a constant temperature, as found by Boyle and 
Mariotte, called Boyle's law, or the first law of dynamics. By 
this law the density of air and the atmosphere under compres- 
sion, whether from the gravity of its own weight or by arti- 
ficial compression, is directly proportional to the pressure to 
which it is subjected, when its temperature is constant or at the 
same temperature throughout the change of volume. It follows 
that when the height above the sea level increases by equal 
intervals and for equal temperatures the density of the air 
decreases in a geometrical ratio: thus, a cubic foot of air at sea 
level will become two cubic feet at about 18,000 feet above the 
sea, and four cubic feet at about 36,000 feet. This condition 

of tenuity of the atmosphere at great heights is shown in 
3 



34 COMPRESSED AIR AND ITS APPLICATIONS. 

the scanty vegetation, and the difficulty of sustaining life in 
the attempts to climb to the dizzy altitudes of our highest 
mountains. 

In the process of compressing air under the ordinary con- 
ditions of the atmosphere, it becomes heated by compression; 
and on cooling in the compressed state becomes saturated by 
the narrowing limits of the moisture or water vapor held in the 
free air ; and on further cooling the excess of moisture is set free 
as water in the reservoirs or pipes containing the compressed air. 

For convenience of reference in regard to the relations of 
air and its contained moisture, the following table shows these 
conditions for differences of io° F. from zero to the boiling- 
point of water : 

Table II. Column 2 gives the comparative volume of free air 
at different temperatures from its volume of 1. at 32 F. 

Column 3. — The weight of one cubic foot of absolutely dry 
air at the temperatures in the first column. 

Column 4. — The elastic force of the vapor of water alone in 
inches of mercury at the temperatures in the first column. 

Column 5.' — -The elastic force of the air alone in a saturated 
mixture of air and vapor in inches of mercury. Its values are 
obtained by subtracting the elastic force in column 4 from the 
standard barometric pressure at sea level; viz., 29.92 — column 
4 = column 5. 

Column 6. — Represents the weight of the air alone in a 
saturated mixture of air and vapor; it is obtained by the 
product of the weight of a cube foot of dry air in column 3 and 
the elastic force of air alone in column 5, divided by the stand- 
col 3 X col ^ 

ard barometric pressure of 29.921 : — — — = col. 6. 

29.921 

Column 7. — -Is the weight in decimals of a pound of vapor 
contained in one cubic foot of saturated air at temperatures from 
o° F. to 212 F., and is obtained by dividing the product of 
column 3 and column 4 by the standard barometric pressure at 
sea level (29.921), and multiplying the quotient by the relative 



THE PHYSICAL PROPERTIES OF AIR. 



35 





« 


Temperature, Fahren- 
heit. 


> 
W 


m O O CO^J OLn* w to i-h 00 oo~j Ou> *• 01 to i-l 

tototototototototototototototototototototoc 


_M H M M H M H _M H M M H H H M H H H _M _ O 

WWWWtOtOtOtOlOi-HMMi-HnOCCOOOOO 
04-toC0004-toOC004-toCC004-tOOOOCM-^ 
»J --J C> Ocn Uiui^i-I-UUBIOUHBOOOOUI 


N 


Volume of dry- 
air at temperatures in 
first column. 


■ 1 

< 




00 


Weight of 

one cubic foot dry air 

at temperature 

in first column. 

Pounds. 


< 


0000-000000000000000000 

t-n OOOCT>OOOOOO^J-~J--J--I^-J~--I^J COOOOOCO 
OOOi-HlOW4-0^4COOOtOW4-O^JOOt04-0 
m O O CO co coo o i-i B4-M OUM h o i-i ^J 4- to 4- 


r 

z g' 

i § 

2 W 


tO tO l-H « M M 


1 


Elastic force 

of vapor alone. 

Inches of mercury. 


O 4- OOO ~J C O i-i -J O-J OcnC^JUlWtOMMOO 
to u to C '~n O W Of-n WWW CO GO Ln CO O CO i-h ^1 4- 
m O CO O ooo OtnMMi-iO^iHN'mCT, co^j m 004- 4- 


2 o 
Tl 




— i-ii-Hl-HtOtOtOtOtOtOtOtOtOtOtOtOtOtOtOtO 

C <-n OU^jo hu m O^J^J oocooOOOOOOO 


o-i 


Elastic force 

of the air alone in 

the mixture. 

Inches 
of mercury-. 


> 

> 
H 
G 

H 

► 
O 


Cfi 


O 4- O O i-i coo ~J m w i-i 004^. oohuu, o-J co oo co 
O^JO O O to O ui OOO COtO tOUl OW On 4^ O 4- -J 
O w w i-h W to i-h OO O O en O O Oui u 4^ O W O ^r 


> co 




o* 


Weight 

of the air in 

pounds. 


< 
re 

¥L 



B 

re 

d 

er 

o 
o 

E 

re 
£ 




oooooooooooooooooooooo 

C i-h to 10 u 4- 4- u> ui ui OOO^J--J^J^J^J cocococo 
• O O O co o to ~J to oo w t_n oo o t04- O oo c to 4- O 
00<-n OOOW vl^4-0 i-h04- O^J ~J O^-t- to m O W 


M C 




^1 


Weight 
of the vapor 
in pounds. 


c > 

7- Z 


oooooocooooooococooooo 

LowtotOMMMOOOOOOOOCOCOCOO 
OOu>OOWOCoCM-nOototO"«COOOCOO 
com m c_n ci4-M4- OmOO to C> M co 04- w to -h o 
to 4- 4- W CO i-h i-h ^-4 W 4- 4- O <-n C> to COtO-t- O O W ^J 
O en to O tO t-n OW O tO O ^J C^Ji-iM^l04-t00O 


to ^ 

^ <! 

o > 
10 -a 

i-i o 
1— 1 f 3 




00 


Total 
weight. 
Pounds. 


1 3 

> j 
1 ^ 


OOOOOOOOOOOOOOOOOOOOOO 

W 4- 4 Unuiui OOOOO^J^J^4--J^I^J Cocooooo 

O M un O to Ui CO O W (_n -J OOO MU W^4 CO O t04- O 

CO 4_ ow c^^J 4- COO O O co ^j toocn to ecu, W' m w 


-to. 


NO 


Weight 
of vapor in one 

pound of 
saturated air. 


0> coto^J4-WtOi>_iOOOOOCCOCOCOO 
-HOtoi-iOi-HtoOHHCo e>4- wtOrHi-iOOOOCO 

~. to C^W W vj 4_ H vim tOOl tOW C>i CO Ln W tO l-H O 
r-r w 4- OU i-h O^J^J coin 4- Co O CO -J i-h O^J4-cnO 
ffi OW O COW en O m 4- W ^J O i-h OOO i-h O <-n <_n to 


> 


m i-h to 4- O O 
►Hnt0W4-'-nC0t0-JO04-O 

h BU4- OXBhui h O t)i0 4- » COW CT> O to 


o 


Weight 

of dry air for 

saturation with 

one pound of 

vapor. 


3 

3" 


O w oo-(_ n m 4i m 4- OO O 4^ W en *J i-h w 004^ n h 
O (Jh O Ctnui COO en O OO O <-n -f- O ^J tOHUln4. 


Z 

H 




_m M to W 4- ^j to 

!-H>-HMt0W4-OCO>-ltJVt0t0OOO 

t: u u 4- w M O hui\OuiU4- C m w o en couioui 
-J to o ooo 4-w [»H4iU4^4- nowui too O to co 


H 


Cubic feet 
of vapor in one po 
of water 
at elastic force 
column four. 


und 
n 


CfQ ^ 

s w 


M^jcootOcnWOOOOOOOCOOOOOOO 


M 



36 



COMPRESSED AIR AND ITS APPLICATIONS. 



weight of pure vapor with air, which is found to be .623 air 
col. 3 X col. 4 



1., viz. 



X .623 = col. 7. 



29.92 1 

Column 8. — Equals col. 6 -f- col. 7 = the weight of one cubic 
foot of saturated air at the temperatures in column 1. 

Column 9. — Shows the weight of the vapor of water in one 
pound of a saturated mixture of air and vapor at the tempera- 
tures in column 1. It is obtained by multiplying the weight of 
the vapor of one cubic foot in column 7, by the volume of one 
pound of air at the corresponding temperature, as found in column 

2, table XIV., or by dividing col. 7 by col. 6: c0 ' ' = col. 9. 

col. 6 

Also, — '— = col. 10, which is the weight of dry air required 
col. 7 

to become saturated by one pound of vapor at the temperatures 

in column 1. 

Column 1 1. — Represents the volume of vapor in cubic feet 

from one pound of water at the elastic force in inches of mercury 



in column 4 ; it is obtained by 



col. 1 1, or 



col. 10 



col. 11 



col. 7 col. 6 

In Table III. is shown the amount of moisture in saturated air 
at pressures below that of normal atmospheric pressure, from 
14.7 to the zero of absolute pressure, in troy grains per cubic 
foot at a temperature of 6o° F. It shows at a glance the weight 
of the moisture in saturated air by the reduction of pressure to 
a vacuum. 



TABLE III. — Absolute Pressure Height of Barometer and Moisture in 
Saturated Air at 6o° F. 



Average 
pressure to 
square inch. 


Barometer, 
inches. 


Troy grains, 
per cubic foot. 


Average 
pressure to 
square inch. 


Barometer, 
inches. 


Trov grains, 
per cubic foot. 


14.7 


29.922 


5.87 


6.0 


12.213 


2-39 


13 


26.461 


5 


19 


5 


10.177 


1.99 


12 


24.425 


4 


79 


4 


8.142 


1-59 


II 


22.390 


4 


39 


3 


6.106 


1. 19 


IO 


20.354 


3 


99 


2 


4.071 


•79 


9 


1 18.319 


5 


59 


1 


2.035 


•39 


8 


16.284 


3 


14 





O 


.0 


7 


14.248 


2 


79 









THE PHYSICAL PROPERTIES OF AIR. 



37 



In Table IV. is shown the great increase in the amount of 
moisture held in saturated air in its rise of temperature from 
32 ° to 94 F. The weight is given in troy grains to facilitate 
computation. 

TABLE IV. — Weight of Vapor in One Cubic Foot of Air When Satu- 
rated between Temperatures of 32 F. and 94 F. 7,000 Troy Grains 
= 1 Pound Avoirdupois. 



Temperature 


Weight, 


Temperature 


Weight, 


Temperature 


Weight, 


Fahrenheit. 


Troy grains. 


Fahrenheit. 


Troy grains. 


Fahrenheit. 


Troy grains. 


32° 


2-37 


56° 


5.18 


76° 


9.60 


35 


2.63 


58 


5-51 


78 


10.19 


33 


2.89 


60 


5.37 


80 


10.81 


41 


3-19 


62 


6.25 


82 


11.47 


44 


3-52 


64 


6.65 


84 


12.17 


46 


3-76 


66 


7.08 


86 


12.91 


48 


4.01 


68 


7-53 


88 


13.68 


50 


4.28 


70 


8.00 


90 


14.50 


52 


4-56 


72 


8.50 


92 


15.33 


54 


4.S6 


74 


9.04 


94 


16.22 



For indicating the atmospheric pressure, the mercurial 
barometer of standard make is the only safe instrument, but 




Fig. i.— aneroid barometer. 

for transportation and reconnoissance the aneroid is easily 
carried and is fairly reliable. 

Its disked and corrugated vacuum chamber is attached to 
the index hand by levers through a toothed sector and held in 
position by a spring for correcting adjustment. The aneroids 
for mining purposes are provided with a special scale to 
indicate pressures from 2,000 or more feet below sea level to 
5,000 or more feet above, and are also provided with a movable 
vernier scale for levelling. 



38 



COMPRESSED AIR AND ITS APPLICATIONS. 



TABLE V. — Height of Barometer, Gauge Pressure, Boiling Temperature 
of Water, and Approximate Height in Feet Above the Level of the 
Sea, Subject to Correction of Barometer for Sea Level. Mean Tem- 
perature of Air, 6o d F. 





ce Si 3 

&s S 


Water 

boils, 

Fahrenheit. 




ll 

P 


of ■ 

rt $ ° 5 

p,ni ^ 


'53 
ceo a> 


'£ u"- 

rr 


30.00 


14-74 


212.2" 





22.73 


II. 16 


198.5" 


7,250 


29.92 


14 


70 


2I2.0 


70 


22.49 


II.04 


198.0 


7,527 


29.62 


14 


55 


211. 5 


333 


22.26 


IO.93 


197-5 


7,797 


29-33 


14 


40 


211. 


590 


22.03 


IO.Sl 


I97.O 


8,067 


29.04 


14 


25 


210.5 


850 


2I.8o 


IO.7O 


196.5 


8,342 


28.75 


14 


11 


2IO.O 


1,112 


21 57 


IO.59 


196.O 


8,620 


28.46 


13 


97 


209.5 


1,396 


21-35 


IO.48 


195.5 


S.8S7 


28.18 


13 


83 


209.O 


1,641 


21.13 


IO.37 


195.O 


9,157 


27.89 


13 


79 


208.5 


1,905 


20.90 


IO.26 


194-5 


9,443 


27.61 


13 


55 


208.O 


2,169 


20.68 


IO.I5 


194.O 


9,719 


27-34 


13 


42 


207.5 


2,436 


20.47 


I0.05 


193-5 


9.987 


27.06 


)3 


28 


207.O 


2,688 


20.25 


9-94 


193.O 


10,268 


26.79 


13 


15 


206.5 


2,956 


20.04 


9.84 


192.5 


10,541 


26.52 


13 


02 


206.0 


3,223 


19.82 


9-73 


192.O 


10,829 


26.25 


12 


88 


205.5 


3,488 


19.61 


9-63 


I9I.5 


11, 108 


25-99 


12 


76 


205.0 


3,752 


19.41 


9-53 


191. 


n,375 


25.72 


12 


63 


204.5 


4,022 


19.20 


9.42 


190.5 


11,659 


25.46 


12 


5o 


204.O 


4,287 


19.00 


9-33 


190.0 


11,933 


25.20 


12 


37 


203.5 


4,556 


18.79 


9.22 


189.5 


12,224 


24.94 


12 


23 


203.O 


4,827 


18.59 


9.12 


189.O 


12, 503 


24.69 


12 


12 


202.5 


5,089 


18.39 


9-03 


188.5 


12,786 


24.44 


12 


00 


202.0 


5,357 


18.19 


8-93 


188.O 


13,071 


24.19 


11 


88 


201.5 


5,625 


18.00 


8.83 


187-5 


13.346 


23-94 


11 


75 


20I.0 


5,895 


17.81 


8.74 


1S7.O 


13,623 


23.69 


11 


63 


200.5 


6,168 


17.61 


8.64 


1S6.5 


13,917 


23-45 


11 


5i 


200.0 


6 ,437 


17.42 


8-55 


186.O 


14,202 


23.21 


11 


39 


199-5 


6, 706 


17.23 


8.46 


185.5 


14,488 


22.97 


11 


28 


199.0 


6,976 


17-05 


8.36 


185.O 


14,763 



The barometric table (V.) is an abstract from the physical 
tables of the Smithsonian Institution, and is approximately 
correct, an extension of the decimals being dropped with the 
intervening numbers for barometric height. The intervals, as 
noted, are so nearly proportional that all the columns may be 
interpolated between the numbers given for any height of the 
barometer or boiling-point of water. The column of gauge 
pressure is also convenient for reference when required. For 
ascertaining differences in height, subtract the height due to 
the observation of the barometer at the lower station from the 
height due to the observed barometer reading at the upper 
station ; the difference is the approximate height between the 



THE PHYSICAL PROPERTIES OF AIR. 39 

stations. The same is also applicable for observation of the 
temperature of boiling water. 

For accurate measurements, there are small variations and 
corrections which must be made for difference of latitude from 
45 and for difference in temperature between the lower and 
upper stations, and a small correction for the lower station, 
which is only appreciable above 1,000 feet. 

These corrections are collated in all their relations in the 
valuable work of the Smithsonian Institution, "Meteorological 
and Physical Tables," to which the author refers for accurate 
survey work. 

CONDENSATION OF MOISTURE BY AIR COMPRESSION AND COOL- 
ING TO NORMAL TEMPERATURE. 

For any hygrometric condition of the atmosphere, the 
weight of water that may be condensed bj' compression and 
cooling the compressed air to its normal temperature can be 
approximately found by simply multiplying the value for 
saturated air in one cubic foot, in Table II., column 7, by the 
hygrometric percentage, and this product multiplied by the 
number of volumes, less 1. 

Table VI. has been computed for the temperatures in column 
1 by the above formula, and as an example for other percent- 
ages and temperatures than found in the table; say, for a 
hygrometric percentage of 86 in free air, when compressed to 75 
pounds per square inch from air at an external temperature of 
62 F. ; we find in column 3, Table VI., at 62 , the weight of 
water in 5 volumes (6 less 1), or cubic feet, to be .004405 pounds 
per cubic foot of compressed air at the point of saturation of free 
air; then .004405 X 86 per cent =.0037883 pounds, which rep- 
resents the weight of water that will be precipitated from 6 
cubic feet of free air at 62 F. when compressed to 75 pounds 
gauge pressure and cooled to normal temperature. From Table 
VI., by interpolation, the amount of condensation of moisture 
may be approximately deduced, from the compression of any 



40 



COMPRESSED AIR AND ITS APPLICATIONS. 



number of cubic feet of free air per minute, at any temperature 
and pressure, when the compressed air is cooled to normal 
temperature. 

TABLE VI. — Showing the Amount of Water that may Condense in 
Pounds per Cubic Foot of COMPRESSED AIR at Various Pressures, 
when Cooled to Normal Temperature, from SATURATED Free Air. 



i 


2 


3 


4 


5 


6 


7 


8 


ft r 


ft 


y 


m 

^ oi 
a oi 


■a A 

E id 

S 2 


v 

N > 


s 


^0 | 


^0 £ 


o 


Hi 


p * 


O VO 


00 


u 





a £ 


ftS, 


" IJ 






e 


E-i 


E-i m 




" 


32° 


F. 


.000912 


.00152 


.002128 


.004256 


.008816 


.020976 


.045296 


42 




.001320 


.00220 


.003080 


.006160 


.012760 


.030360 


.065560 


52 




.001881 


.003135 


.004389 


.008778 


.018188 


.043.263 


•093423 


62 




.002643 


.004405 


.006167 


.012334 


•025549 


.060789 


.131269 


72 




.003663 


.006I05 


.008547 


.017094 


•035309 


.084249 


.181929 


82 




.005001 


.008335 


.011669 


.023338 


•048343 


.115023 


.248383 


92 




.006750 


.OII250 


•015750 


.031500 


.065250 


■155250 


•335250 



The approximate percentage of water vapor in free air may 
be applied to the tabular figures, for the approximate weight 
of condensation for any hygrometric condition of the atmos- 
phere for intervals of 10 degrees from 32 to 92 F. Barometer 
29.92 inches. 

For example : 500 cubic feet per minute at atmospheric tem- 
perature of 6y° F., compressed to 75 pounds per square inch. 
Free air at 75 per cent, of saturation, which is about the mean 
condition of the atmosphere at or near sea level. Omitting the 
small increase in the ratio of saturation for the rise in tempera- 
ture, the mean between 62 ° and 72 ° in column 3 will be found 
to be .00525 X -75 for the percentage of saturation = .0039375 X 
500 cubic feet = 1.968 pounds of water condensed per minute. 

For any other pressure than stated in Table VI., use the 
proportional difference between the stated amounts in the 
columns next to the required pressure for the approximate 
amount of condensation ; also the rule as stated for any pressure. 



Chapter III. 



AIR IN MOTION AND 
ITS FORCE 



AIR IN MOTION AND ITS FORCE. 

The power of air in the force of the wind was probably the 
earliest of the forces of nature captured by mankind and utilized 
in moving the first sail on the sea, and by its progressive use 
has contributed its vast power to extend the civilizing influence 
of commerce to every part of the world. Nor is its power 
confined to the gentle winds that waft the sails or turn the 
windmills ; its terrors in the storm and the tornado are in con- 
stant evidence. 

In our every-day uses the power of air is what we make it : 
we compress it, we bottle it up under vast pressures, in which 
its power is a potential element ready for work at our bidding. 

The force of air in motion, the wind, was for ages the 
dominant power, and windmills dotted the land in all civilized 
countries. There was a time when the natural forces of wind 
and water were the only ones at the command of man for 
industrial purposes, and when the motors driven by these 
forces monopolized all industrial pursuits which man did not 
accomplish by his own physical exertion. It is still largely in 
use, and is probably the most economical power available 
within its limited sphere of action ; it is obtainable in all parts 
of the world ; the wind blows over every country. 

VELOCITY AND PRESSURE OF THE WIND. 

Observations on the velocity and pressure of the wind have 
been made under varying conditions as high as 159 feet per 
second, with a pressure of 57.75 pounds per square foot, from 
which it was found that the resistance to air in motion varied 
as the square of the velocity nearly, on surfaces with planes at 
right angles to the direction of the wind. 



44 



COMPRESSED AIR AND ITS APPLICATIONS. 



For inclined surfaces the resistance was found to be 1.84th 
power of the sine X the cosine of the angle. 

The pressure of the wind varies slightly for given velocities 
with its density and temperature; so that with a high baro- 
metric pressure and low temperature, say for above 30 inches, 
the formula .005 X area X square of the velocity in miles per 
hour may be used for the pressure per square foot, or .0023 X 
area X square of the velocity in feet per second = pressure in 
pounds per square foot. 

For mean barometric pressure and temperature of 35 ° F., 
.005 X the square of the velocity in miles per hour is in use, 
and from which the wind pressures in the following table, 
Table VII., have been computed. Also -y/200 P = V., in which 
P = pressure in pounds per square foot, and V = velocity in 
miles per hour. 



TABLE VII.— Velocity and Pressure of the Wind. At a Barometric 
Pressure of 29.921 and Temperature of 32° F. 





Veloci 


Y. 




J cjfi 


Observed 


Velocity. 









u 


u 


,. 






Observed 


7~^ 


ft-g 


•©■a 

-M O 


character of the 
wind. 


to 3 


6 
£3 


5) -a 

ftc 

4) O 


m 3 3 


character of the 
wind. 
















0) 0) 






ft 


^ ~ 


fc M 


ft 




ft 


fe H 


fe M 


ft 




I 


33 


1-47 


0.005 


Barely observed. 


16 


I,403 


23.48 


I. 291 




2 


176 


2-93 


.020 


Just perceptible. 


17 


1,496 


24-93 


1-453 




3 


264 


4.40 


• 045 


Very light. 


18 


1,534 


26.40 


1-634 




4 


352 


5.S7 


.081 


Light breeze. 


iq 


1,672 


27.86 


I. 821 




5 


440 


7-33 


.126 


Fair breeze. 


20 


1,760 


29-33 


2.0I8 




6 


52S 


8.8O 


.181 


Very fair breeze. 


25 


2,200 


36.67 


3-155 


Very brisk. 


7 


616 


10.27 


■ 247 




30 


2,640 


44.00 


4-547 


| High wind. 


8 


704 


"•73 


• 323 


Fresh breeze. 


35 


3,080 


51-33 


6.194 


9 


792 


13.20 


.408 




40 


3.520 


58.67 


8.099 


Verv high wind. 


10 


S80 


14.67 


.505 


Strong breeze. 


45 


3,9°o 


66.00 


10.260 


Gale. 


11 


968 


16. 13 


.610 




50 


4,400 


73-33 


12.684 


Storm. 


12 


1,056 


17.60 


.726 




60 


5,280 


88.00 


18.310 


Great storm. 


13 


1. 144 


19.07 


.852 




80 


7,040 


"7-3 


32.80 


Hurricane. 


14 


1,296 


20.53 


.988 




90 


7,920 


132.0 


40.50 


[ Tornado. 


15 


1,320 


22.00 


1. 135 


Stiff breeze. 


100 


8,800 


146.6 


50.00 



There is a variation in pressure, due to temperature, 
amounting to about 1.7 per cent of the tabulated pressures, 
which are additive below 32 F., and subtractive above, for 
each io° F; so that in a hurricane at 80 miles an hour, with the 




AIR IN MOTION AND ITS FORCE. 45 

thermometer at 90 , the pressure would be 29.16 pounds per 

square foot, instead of 32.8 in the table. 

The wind pressure on spherical surfaces is approximately 

0.36, that on a plane circular surface of the same diameter, as 

in Fig. 2. On a cylindrical surface of a length 

I 
equal to its diameter the wind pressure is equal f 

to 0.5 that on a plane surface equal to the diame- 
ter and length of the cylinder ; hence the power 
that operates the cupped or curved blade ane- 
mometers and horizontal windmills. The curved 
blades, as shown in Fig. 3, represent the prin- ^^7™!*° 
ciple of the action of the wind on curved surfaces. 
As a windmill, this form, as well as mills made with flat, in- 
clined blades revolving on a vertical axis, are very much weaker 
in power than the vertical plane form, as shown in Fig. 5, 
which has been found to possess a higher efficiency than any 
of the windmills of other forms. 

The measurement of the velocity and force of the wind is 

approximately obtained by the use of anemometers of various 

kinds for the velocity and by resistance planes for its force. 

The Robinson four-armed cup form, used by the United States 

Weather Bureau, is generally accepted as the best form for a 

I stationary anemometer. The small Davis or 

+ Biram windmill anemometers, with gear and 

X~ry dials adjusted for indicating the velocity of air 

&? currents in mines or ventilating passages, are 

^3 cC much in use and fairly reliable. 

^)J\^ With the cup anemometer the experiments 

fig. 3.-anemom- of Dr. Robinson and others on the difference 
in force of the wind upon the spherical and 
hollow side of a cup resulted in finding that the pressure for 
all wind velocities was four times as much on the concave side 
as upon the convex side. 

By differentiating the pressures, it was found that the 
velocity of the wind was about three times the velocity of the 



46 



COMPRESSED AIR AND ITS APPLICATIONS. 




-ROBINSON'S ANEMOMETER. 



centre of the cups, not including the friction, which is a 
variable factor to a small extent, slightly increasing with 
the velocity of the wind. The ratio for the differential 
pressure and friction in the standard cup anemometers of 4 

inches cup diameter and 7-inch ra- 
dius to their centres, is 3, from 
which their dial gear is computed. 

In Fig. 4 is shown the general 
construction and arrangement of 
the index train of a Robinson ane- 
mometer. Each dial is graduated 
respectively to 0.1 mile, 1 mile, 10 
miles, 100 miles, 1,000 miles, and 
these revolve behind fixed indexes, 
the readings of which are taken according to the indication on 
the faces under the indexes. Observations are recorded by dif- 
ferentiating the readings of the dials and multiplying by the 
observed time. A most convenient way is to record the read- 
ings of the dials at intervals of 12 minutes and divide their 
difference by 10 for the velocity of the wind in miles per hour. 
The Biram anemometer (Fig. 5) is much in use for testing 
the velocity of the air current in the ven- 
tilation of mines, hospitals, schools, and 
public buildings. 

For testing the volume of air passing 
in a ventilating flue or air-shaft of a mine, 
select a place having a uniform section ; 
let the instrument run a short time to 
gain full speed ; then test it one minute by 
a watch and note the velocity, as indicated 
by the difference of the two dial readings 

at the beginning and end of a minute; then multiply the area 
of the flue or air-shaft in square feet by the velocity in feet 
per minute for the cubic feet per minute. In some of the 
States the law requires a supply of 100 cubic feet of air per 




BIRAM ANEMOM- 
ETER. 



AIR IN MOTION AND ITS FORCE. 



47 



man per minute, and as much more as the special condition of 
the mine may require. 

The direct pressure of air currents up to about 6 inches for 
water, or yVifo" °f a P oun d per square inch, and indicating 
velocities up to near 80 miles per hour, is readily obtained by 
Lind's siphon pressure gauge, shown in Fig. 6. It consists 
of a glass siphon, with parallel limbs, mounted upon a vertical 
rod, on which it moves freely by the action of the vane which 
surmounts it. The upper part of one of the limbs is bent out- 
ward toward the wind. Between the limbs is a graduated 
scale, indicating from o to 3 inches in 
ioths, the zero being in the centre of 
the scale. In use, the tube is filled 
with water to the zero of the scale and 
exposed to the action of the wind, by 
which the water is depressed in the 
one limb and raised in the other. 
The sum of the elevation and depres- 
sion is the height of the column which 
the wind is capable of sustaining. 

The pressure indicated is .036 of 
a pound per square inch per inch of fig. 6. -the siphon pressure 

GAUGE. 

difference in the level of the two legs 

of the siphon, or 5.18 pounds per square foot. Then each 
division of one-tenth of an inch will represent .518 of a pound 
per square foot, and by reference to the wind-pressure column 
in Table VII. the approximate velocity of the wind for any 
pressure may be found. This also corresponds with the veloci- 
ties derived from water pressure in Table X. 

The capacity of air for evaporating water varies greatly, 
depending upon the temperature of the water, the relative 
temperature of the air, its humidity, and its velocity over 
the surface. These four conditions vary the effect one with 
another, so that from the following table of observed evapora- 
tion for even temperatures of both air and water and for 




48 COMPRESSED AIR AND ITS APPLICATIONS. 

degrees of humidity by tenths, a fair estimate may be made for 
different conditions: 



TABLE VIII. — Evaporation at Even Temperatures of Water and Air 
and at Different States of Humidity of the Air, in Grains per 
Square Foot per Hour, in Calm Air. (Box.) 



Tempera- 




Humidity 


df the Air ; Saturation = 1 






















of air and 


















water. 


Dry. 


3° 


40 


50 


60 


70 


80 


90 


32° F. 


69 


48 


41 


34 


28 


21 


14 


7 


42 


IO.I 


71 


61 


51 


40 


30 


20 


10 


52 


147 


103 


88 


74 


59 


44 


29 


15 


62 


211 


148 


127 


106 


84 


63 


42 


21 


72 


298 


209 


17S 


149 


119 


89 


60 


30 


82 


426 


298 


256 


213 


170 


128 


85 


43 


92 


570 


400 


342 


285 


22S 


171 


114 


57 



From experiments by Dr. Dalton, the increase of evapora- 
tion from a calm by a light wind of three or four miles per 
hour made an increase in the evaporation of 28 per cent, and 
from a fresh breeze of about 8 miles per hour made an increase 
of evaporation of 50 per cent for air of nearly the same tem- 
perature of the water. A warmer wind than the water will 
somewhat increase the evaporation and a colder wind will 
retard it. 



Chapter IV. 



AIR PRESSURES 

BELOW 

ATMOSPHERIC PRESSURE 



AIR PRESSURES BELOW ATMOSPHERIC PRESSURE. 

A vacuum is the zero of atmospheric pressure, and is the 
beginning from which the absolute- pressures start in many air 
problems; and, like the absolute zero of temperature, it is the 
point in the scale of pressure at which air expansion becomes 
infinite, and to which temperatures contract to the measure of 
interplanetary space. 

One of the means by which the pressure of the atmosphere 
is reduced toward a vacuum is an air pump (Fig. 7). Its 
power to produce negative atmospheric pressures to a certain 
extent is complete ; but is limited in ultimate results by the 
amount of the volume of clearance divided by the volume of 
the piston stroke. 

At the point of the greatest exhaustion by an air pump the 
clearance volume expands by its elasticity as the piston recedes 
and fills the entire cylindrical space, so that the best mechanical 
pump can scarcely produce a vacuum of less than one-hundredth 
of an inch of mercury, and often one-tenth of an inch is the 
limit. Preferring to the cut, the pump consists of two cylinders 
with pistons operated by racks on each side of a pinion and the 
oscillating motion of the handles M N. Each piston has a 
valve opening upward, and the base of the cylinder also has a 
valve opening upward at c\ the cock at Q is to shut off one of 
the cylinders, and a cock at 5 shuts off both cylinders to 
prevent leakage ; r is a relief valve. At T is a cock to shut off 
the mercury gauge E, which is a U-shaped glass tube with one 
end closed and the tube partly filled with mercury, and with a 
Torricellian vacuum in the closed end, and a gauge attached ; 
the whole enclosed in a glass cover and connected with the 
cock T. The platform V is arranged to seal by contact the 



5- 1 



COMPRESSED AIR AND ITS APPLICATIONS. 



various implements used in experimenting on the properties of 
air below atmospheric pressure. 

The hydraulic air ejector, Venturi vacuum pump, or aspi- 
rator, is a most convenient instrument for quickly obtaining an 
approximate vacuum. In its construction the form of the 
curved nozzles is made after the suggestions first enunciated 
by Venturi, on the principle that a passing fluid at a high 
velocity through a converging and a diverging nozzle, in which 




THIC AIR PUMP. 



the curves conform to the shape of the vena contracta of a jet 
from an orifice, will produce an approximate vacuum at a point 
near its greatest contraction, and if an air chamber is connected 
through an orifice at this point, the air will be discharged and 
nearly a perfect vacuum will be made in the air chamber. The 
water-entering nozzle may be connected by a rubber tube to 
any faucet of a town water-works, or from a tank having a head 
of more than 14 feet, or one-half the static water-head of a 
vacuum. The air-inlet leg requires an elastic valve, as shown 
in the cut, and a small bar occupying nearly one-half the area 



AIR PRESSURES BELOW ATMOSPHERIC PRESSURE. 53 

of the water-exit end has been found necessary in practice for 
its more perfect action. The cut is an exact proportional form 
and one-half the dimensions of those in use in laboratory and 
experimental work. It is capable of producing a vacuum equal 
to the barometric height, less the height due to the tension of 
the vapor of water, which at 6o° F. equals one-half inch of 
mercury ; while at the temperature of the greatest density of 
water, a vacuum ranging within one-quarter of an inch of the 
barometric height due to the atmospheric pressure may be 
obtained. 

The aspirator for various purposes has been made in several 
forms, following the principles of the hydraulic ejector and the 
steam injector for large volumes ; but for general utility, this 
simple form has come into use for 
experimental work in educational 
institutions, and in the arts where 
an automatic and constant vacuum 
draft is needed. The aspirator is 
made by Mr. E. C. Chapman, 287 
Gates Avenue, Brooklyn, N. Y. 

For a more perfect vacuum than FlG 8 ._ VENTURI VACUUM PUMP . 
the air pump or the hydraulic aspi- 
rator gives, the Sprengel mercurial air pump is found to produce 
nearly a Torricellian vacuum. One of the many forms of this 
pump we illustrate in Fig. 9, which can be readily constructed 
by any amateur of ordinary genius. The individual tubes are 
shown in the section to the right of the assembled instrument. 

The materials necessary for the construction are as follows : 
A piece of soft glass tubing 5 ft. long, with a bore of about f of 
an inch (1 centimetre) ; three pieces, each 5 ft. long, with a 
bore of -^ of an inch, having fairly thick walls, say -^ of an 
inch. If the bore is much over -^ of an inch, the pump will 
not produce a good vacuum. Two or three feet of thick rubber 
hose to connect the pump with the vessel to be exhausted ; a 
quart bottle, with the bottom cut off, and a brass screw clamp. 



54 



COMPRESSED AIR AND ITS APPLICATIONS. 



The large tube is to be drawn down to half its diameter 
about an inch from one end. The bore of this contracted 
portion should be too narrow to admit one of the smaller tubes. 
This allows of a cement joint of good sealing-wax, or a mix- 
ture of pitch and gutta-percha. The exhaust tube E should be 
joined to the c7bend at B by welding the glass. The clip on 
the rubber connecting-piece at D serves 
to regulate the flow of the mercury 
through the small tube within the large 
tube, and which should extend about 
2 inches below the scale. The long- 
leg of the large tube may be 36 inches 
in length. The U bend at B should 
be on a level with the zero mark on 
the inverted 30-inch scale. A small 
cup seals the end of the small tube at 
G. The overflow of mercury falling 
into the receptacle below, allows of its 
transfer to the bottle above through a 
funnel and filter of paper perforated 
at the bottom. The apparatus may be 
arranged on a board and the whole ap- 
portioned by the inch scale, as shown 
in the figure. R represents the attach- 
ment of a radiometer or an incandes- 
cent lamp, and i^that of a Geissler tube. 
To run the apparatus a good-sized cup 
of mercury will be required. The more mercury there is the 
less trouble there will be in continually transferring it from 
the basin to the reservoir. Close the clamp first, also stop the 
exhaust tube at E, then pour the mercury into the funnel. It 
will run through in a few minutes, leaving a black scum on 
the paper unless pure. Now open the cock a little and the 
tubes begin to fill, the fluid rising in a double column in the 
large and small tubes. As soon as it reaches the Tit will flow 




-MERCURIAL AIR PUMP. 



AIR PRESSURES BELOW ATMOSPHERIC PRESSURE. 55 

over and down, dragging air from the exhaust tube. Stop the 
flow. You will notice that the column in the large open tube 
does not rise above the T; hence it cannot overflow. Make a 
paper scale, divided into 30 inches, and duly marked; paste 
this beside the large tube, so that the top of the scale is oppo- 
site the top of the mercurial column. Everything is now ready 
for the process of exhaustion. Connect the exhaust tube with 
the vessel (say a Geissler tube, F) by means of a piece of rubber 
tube, which should fit very tightly over the tubes. Open the 
clip a little and the drops of mercury immediately begin to 
tumble over the bend and go chasing each other down the long 
tube. They should go over quite slowly, say two a second, and 
the spaces between them will be quite long at first. Notice 
the mercury column in the large tube ; it is falling rapidly, and 
by observing the scale you may know exactly how the exhaus- 
tion is proceeding. When the column reaches the 15 -inch 
mark, exactly one-half of the air has been removed from the 
vessel. As the exhaustion proceeds, the air between the 
falling drops becomes thinner and thinner, and finally we have 
a solid column in the long tube, standing 30 inches above the 
surface of the cup G, upon which the drops fall with a sharp 
metallic click, and the column of mercury in the large tube 
will stand at the index of the barometric pressure. This ham- 
mering of the pump shows that the exhaustion is very perfect, 
the air being too thin to serve as an elastic cushion. The 
pump should be allowed to hammer away for a few minutes, 
when the vessel may be disconnected, either by fusing the 
glass tube connecting it with the hose or in any way that is 
desired. Care must be taken to keep the reservoir supplied by 
transferring the mercury from the basin to it. It is best to 
have two basins, and exchange them at intervals. With this 
pump, Geissler and Plucker tubes, or small electric light bulbs, 
may be exhausted, and any experiments requiring high vacua 
may be performed. A vacuum of 5-0 0,000,000 °f an atmosphere 
is claimed to have been made with this form of Sprengel pump. 



5^> 



COMPRESSED AIR AND ITS APPLICATIONS. 



The general principles of the combined condenser and air 
pump are shown in Fig. 10, in which A is the exhaust inlet to 
the condenser F, B the water inlet, and D the spray valve, 
which is adjusted by the valve wheel on the valve spindle at 
E, G the pump piston, H the suction valves, and / discharge 
valves; K, steam chest and valve. 

In this class of injector condensers, from 27 to 30 times the 
weight of steam used in the engine must be furnished in water 
to the condenser. For instance, if an engine is using 20 
pounds of steam per horse-power per hour, then 540 or more 

pounds of water, or 72 or more 
gallons of water per hour, must 
be provided for effectual con- 
densation. The capacity of the 
air pump should exceed the 
water volume by about 50 per 
cent for effectual work and for 
maintaining a vacuum of 24 to 
26 inches of mercury. 

The steam vacuum or air 
pumps, as now constructed, of 
which Fig. 1 1 is a representa- 
tive air pump and jet conden- 
ser, made by Guild & Garrison, and Fig. 12 is a vacuum pump for 
the work of evaporation in vacuum pans, enables the produc- 
tion of a vacuum within one inch of the barometric height, and 
will maintain a vacuum of two inches less than the barometric 
height for steam power with a good condenser. 

For evaporating and concentrating liquids and syrups, there 
is a considerable range in the amount of water that can be 
evaporated from various kinds of liquids and substances, owing 
to their degree of viscosity, which property seems to have a 
holding power on the water with which they are combined or 
saturated. The evaporation of natural water at normal tem- 
peratures under reduced atmospheric pressure is largely 







CoNliKNSKR AND PUSH 



AIR PRESSURES BELOW ATMOSPHERIC PRESSURE. $7 

increased from the conditions and temperatures shown in Table 
VIII. for open-air evaporation. 

The experiments of Daniell show that the evaporation of 




Fig. ii— guild & garrison air pump and jet condenser. 

water is nearly inversely proportioned to the pressure, so that 
at half the normal pressure the evaporation would be doubled. 
With a vacuum as nearly perfect as could be obtained, or ¥ -|- ¥ 
of a normal barometric pressure, the evaporation is increased 



53 



COMPRESSED AIR AND ITS APPLICATIONS. 



about 70 times more than would be due to the evaporation at 
normal atmospheric pressure. 

Referring to Table VIII. as a gauge for open-air evaporation, 




471 



Fig. 12.— vertical double-acting air pump and jet condenser. 
One of several types built by the Dean Brothers Steam Pump Works, Indianapolis, Ind. 

and using the third column as representing the conditions at 
one-half atmospheric pressure, or barometer at 15 inches, tem- 
perature 62 , we would have an evaporating effect of 296 grains 
of water per square foot of surface per hour. The distillation 



AIR PRESSURES BELOW ATMOSPHERIC PRESSURE. 



59 



of water at higher temperatures and under a higher vacuum 
with a surface condenser is a most important item in the pro- 
duction of artificial ice, and by reducing the vacuum to |~£ and 
heating the water to its boiling-point under the vacuum, say 
1 14 F., from 8 to 10 pounds of water may be evaporated per 
square foot of surface per hour. 

TABLE IX. —Boiling and Vaporizing Temperatures of Water, At and 
Below Atmospheric Pressure, with Pressures and the Volume of One 
Pound of Vapor. (Claudel.) 





Pressure. 


Volume of 


Tempera- 


Pressure. 




Tempera- 










Volume of 


ture, 




Per 


one pound, 


ture, 




Per 


one pound, 


Fan. 


Mercury, 


square 


cubic feet. 


Fah. 


Mercury, 


square 


cubic feet. 




inches. 


inch, 
pounds. 






inches. 


inch, 
pounds. 




211° 


29.92 


14.70 


27.2 


120° 


3-43 


1.68 


204.9 


2IO 


28.75 


14.12 


28.2 


115 


2-97 


I.46 


234-7 


205 


25-99 


12.77 


31.0 


no 


2-57 


I.27 


268.I 


200 


23.46 


11-52 


34-1 


105 


2.23 


I.09 


307.7 


195 


21.14 


IO.38 


37-6 


100 


1. 91 


•94 


353-4 


190 


19.00 


9-33 


4i-5 


95 


I.64 


.81 


408.2 


185 


17.04 


8-37 


45-9 


90 


1. 41 


.69 


471-7 


180 


i5- 2 9 


7-5i 


50.8 


85 


1.20 


■59 


549-5 


175 


I3-65 


6.71 


56.4 


80 


1.02 


•50 


641.0 


I70 


12.18 


5.98 


62.4 


75 


.87 


•43 


746-3 


165 


10.84 


5-33 


69.8 


70 


•73 


■36 


877.2 


160 


9-63 


4-73 


75-0 


65 


.62 


•30 


1031.0 


155 


8-53 


4.19 


87-3 


60 


■5i 


• 25 


1220.0 


I50 


7-55 


3-71 


97.8 


55 


.42 


.21 


1429.0 


145 


6.66 


3-27 


110.0 


50 


.36 


.18 


1695.0 


I40 


5-86 


2.88 


124. 1 


45 


•30 


•15 


2041.0 


135 


5-17 


2-54 


140. 1 


40 


■ 25 


.12 


2439.0 


I30 


4-51 


2.21 


158.7 


35 


.20 


.10 


2941.0 


125 


3-93 


i-93 


180.5 


32 


.18 


.09 


3226.0 



The steam or other power vacuum pump is the means of 
utilizing the work from a vacuum for commercial purposes. 

Their use is a source of economy in all operations requiring 
a large amount of air to be withdrawn from an evaporating 
apparatus or to keep up the greatest tension possible when a 
large quantity of water is used for condensation, as it has been 
shown in previous chapters that water in its natural condition 
holds a considerable amount of air, which becomes liberated 
under a vacuum ; hence the necessity of the use of a large 
vacuum pump where jet condensation is used. 

In Fig. 13 is shown a vacuum pump of the Guild & Garrison 
type, much used in operating the triple effect sugar trains. 



6o 



COMPRESSED* AIR AND ITS APPLICATIONS. 




AIR PRESSURES BELOW ATMOSPHERIC PRESSURE. 



6 1 



The large air head on this class of pumps is for the purpose of 
arranging the inlet and outlet valves above the cylinder, and 
to allow the clearance to be charged with solid water and to 
retain it, so that there shall be a perfect exit of the air above 
the water. To prevent shock by the water striking a level 
valve plate and to leave no space that can retain air, the exit- 




FlG. 14.— VACUUM PUMP CHAMBER. 

valve plate is placed in an inclined position, as shown in Fig. 
14, which allows every fraction of space to be closed by the 
clearance water at the end of each stroke of the pump. 

In the "wet system" all the water used for condensation 
passes through the pump, while in the " dry system " the 
barometrical column, or leg pipe, carries off the injection water 
by gravity from the bottom of the condenser without passing 



62 



COMPRESSED AIR AND ITS APPLICATIONS. 












-: * 



'l 'fs 



AIR PRESSURES BELOW ATMOSPHERIC PRESSURE. 63 

through the pump. The combined vacuum and water pumps 
are so arranged that when connected with a vacuum pan work- 
ing on the "dry" system, the water cylinder of the pump is 
connected to deliver the injection water to the tank that feeds 
the condenser, or, if preferred, to the condenser direct. In 
Cuba and other places where the "cooling tower" is in vogue 
(the injection water being used over and over again), the water 
cylinder is arranged to take the warm water discharged by the 



^r- 





-CLAYTON STEAM ACTUATED VACUUM PUMP. 



air cylinder and deliver it to the "cooling tower." This is the 
general arrangement when working on the "wet" system. 

Fig. 16 represents the duplex vacuum pump of the Clayton 
Air Compressor Works, New York City, in sizes ranging from 
4-inch to 16-inch diameter of vacuum cylinder, with corre- 
sponding steam cylinders of less size ; stroke from 3 to 1 5 
inches. They are constructed with water-jacketed vacuum 
cylinders when desired. 

Poppet valves are placed in the heads of the cylinders. 
Single vacuum pumps are made of the same sizes. 

The Blake duplex fly-wheel vacuum pump is illustrated in 



64 COMPRESSED AIR AND ITS APPLICATIONS. 

Fig. 17, in which the design of the vacuum cylinder and valves 
is such that the same pump may be used equally well for the 
wet or dry system of evaporation. 



THE COMMERCIAL UTILITY OF A VACUUM. 

The history of the vacuum in the United States Patent 
Office is an interesting one, dating back to 1833, in which year 
George H. Richards took out exclusive rights in a process for 
preparing leather from various substances by evaporation in 
vacuo at a temperature below 2 12 , the object being to avoid 
injuring the product by too great heat. This method is 
applied in obtaining flavors for sirups dispensed at soda-water 
fountains. It also serves in making extracts from malt and 
hops and from coffee. The fact is well known that firms 
engaged in the business of roasting coffee for market commonly 
deprive the beans of their volatile flavoring essence and sell the 
latter separately. An honest coffee roaster returns this essence 
to the beans. Much of it passes off during the ordinary cook- 
ing process, and thus it happens that at times the streets in the 
neighborhood of a coffee-roasting store are fragrant with the 
odor of coffee. It is agreeable to the nostrils, but very waste- 
ful. A properly constructed roasting-machine saves and con- 
denses the vapor. 

Bakers use great quantities of egg meats dried in vacuum 
pans. The eggs are broken into the pans, the whites and 
yolks being separated. They are then evaporated to dryness, 
after which they are scraped from the pans and granulated by 
grinding. The product looks very much like sawdust; it is 
comparatively cheap, and will keep good for many months, 
taking the place of fresh eggs when the latter are scarce and 
dear. A similar process is employed in the manufacture of 
so-called "egg albumen," which is said to be composed largely 
of the whites of eggs. It looks like a fine quality of glue, 
being used by bakers and for glazing. 



AIR PRESSURES BELOW ATMOSPHERIC PRESSURE. 



65 



Several processes have been patented for preserving eggs 
in their shells by means of the vacuum. One method is to place 
them in a chamber, which is then exhausted of air. The air, 



% 




containing the germ of decomposition, is thus drawn out of the 
eggs, and carbonic acid gas is forced into the receiver to take 
the place of it. A variation of this idea is to introduce into the 
receiver melted paraffme, which fills the pores of the shells. 



66 COMPRESSED AIR AND ITS APPLICATIONS. 

Eggs are canned by the vacuum process, being heated some- 
what to preserve them, but the temperature to which they are 
rased cannot be high, for the white hardens at 140 F. 

There are numerous patents for preserving foods with the 
aid of the vacuum. One idea is to extract the air contained in 
the meat, fish, and fruit, which are to be impregnated there- 
upon with a solution of gelatine. This being accomplished, 
the meat is to be taken and dipped into a solution of gelatine, 
sugar, and gum, so as to give it a coating on the outside. 
Thus it will keep for an indefinite period. 

Vacuum processes are to-day largely and successfully 
employed in the salting and pickling of meats' and vegetables. 
They are shut up in chambers from which the air is withdrawn, 
and brine is then forced in under pressure. The meat is some- 
times stuck full of tubular perforated skewers, to permit the 
gases to escape and to admit the brine to all parts of the 
substance treated. Another method adopted is to withdraw 
the brine with the air pump and force smoke into the meat, 
which is thus smoked as well as salted. On this idea there is 
an improvement, which consists in utilizing a smoked brine. 
This is prepared by withdrawing the air from a tank contain- 
ing the brine and forcing the smoke into it under pressure. 
Then the smoked brine is applied to the meat. 

Methods are used on a considerable commercial scale for 
preserving meats and vegetables by withdrawing the air from 
them and substituting various gases, such as nitrogen and car- 
bonic acid gas. Argon has not been suggested for the purpose 
as yet, but before long it will be, doubtless. In 1853 Henry 
Hunt took out the first patent for employing the vacuum in 
canning fruit products, such as would suffer injury from heat- 
ing. His idea was to exhaust the air from the cans in order 
that no germs of putrefaction might remain. A singular adap- 
tation of the same notion is credited to N. Raymer, of New 
Sterling, N. C, who invented a fruit-jar stopper with a short 
metal tube attached to it. The housewife, when she has closed 



AIR PRESSURES BELOW ATMOSPHERIC PRESSURE. 6j 



^ftfrj 




Fig. 18— thk vertical twin air pump. 
Blake pattern for marine service. Single acting beam. G. F. Blake Mfg. Co., N. Y. City. 



__ 



68 COMPRESSED AIR AND ITS APPLICATIONS. 

a filled jar of fruit with such a stopper, has only to draw a 
partial vacuum by applying a small pump to the tube, and 
pinch it with pliers, fusing the end with a hot iron to make it 
air-tight. 

The evaporation of fruits and vegetables is a most important 
industry, and owes its finest output to the vacuum process. 

The vast sugar-refining interests of the world are dependent 
upon the vacuum process for success in the quality of this, the 
sweetest element of domestic use. 

The condensation and preservation of milk has become a 
large industry in Europe and the United States, and its per- 
fection is greatly due to the vacuum process of evaporation. 

One of the most useful applications of the vacuum has been 
for the preservation of wood. Scores of patents in this line 
have been granted. So far back as the year 1837 August 
Gotthilff, of New York, secured exclusive rights in a process 
for " protecting timber from destruction by worms, dry rot, and 
other causes of spontaneous decay." His idea was to exhaust 
the air from the wood and fill up the pores with coal tar and 
turpentine. In this direction a great industry has since grown 
up. Piles and railway timbers are impregnated with preserva- 
tive substances ; while metallic solutions are employed by the 
vacuum process to defend our wooden ships against the 
depredations of the devouring shipworm or teredo. 

Wood is artificially colored by using the vacuum to with- 
draw its fluid juices, the place of which is filled with solutions 
containing pigments. In this manner ordinary pine may be 
beautifully stained and made to serve as a substitute for rare 
and costly wood. Lumber is seasoned offhand by exhausting 
the air from it, and then forcing dry air through the pores to 
carry off the moisture. Wood is hardened for all sorts of pur- 
poses, from bridge-making to wagon-making, by a vacuum and 
pressure process called "vulcanizing." 

The variety of purposes to which a vacuum may be applied 
seems almost endless, and again we continue the enumeration 



AIR PRESSURES BELOW ATMOSPHERIC PRESSURE. ■ 69 

of lifting of acids and other fluids, exhaust filters, the transfer 
of sewage from cesspools to closed tanks on wheels for removal, 
by the vacuum process. 

The operation of the pneumatic tube system for cash, tele- 
graph, and postal service has become a most important item for 
the rapid transportation of mail matter. 

A system of transmitting power to small uses by a vacuum 
pipe system was tried in Paris, France ; but was discontinued 
or changed to the compressed-air system. The great forte 
in the usefulness of the vacuum has been found in the low- 
pressure system of steam power, which owes to the vacuum the 
immense development in the steam motive power of the present 
time. Our immense steam marine owes its wonderful economy 
of one pound of coal per hour per horse-power to compounding 
with triple and quadruple effect derived from the ultimate 
vacuum. The manufacture of ice by the vacuum process has 
been accomplished, and rooms have been cooled by air circula- 
tion around chambers of ice frozen by a vacuum process. 

DRYING IN VACUO. 

A vast saving in the economic values of many by-products, 
consisting of wet grains from breweries, distilleries, etc., and 
of root chips from beet-sugar manufactories, form, in many 
cases, food-stuff of value ; but on account of the great quantity 
of water they contain, they are subject to rapid destruction by 
decomposition, and their nutritious qualities, especially, suffer 
most. The same cause also prohibits their carriage over any 
great distance. In the case of wet beer grains, for instance, 
carriage has to be paid for about 75 per cent, of water. Hith- 
erto, therefore, it has been necessary to utilize these by- 
products on the spot where they are produced, or at least in 
close proximity thereto, as well as with the least possible delay. 
The natural consequence is a low price for such products, of 
which, moreover, the supply is often greater than the demand, 



■JO COMPRESSED AIR AND ITS APPLICATIONS. 

and thus prevents their realizing anything like their market 
value, particularly during the hot summer months, when plenty 
of other food-stuff is to be had. The old plan of preserving 
such perishable substances in pits or silos is only a very rough 
and poor remedy and does not answer its purpose at all com- 
pletely; for, notwithstanding all precautions, decomposition 
sets in, and a loss of as much as 50 per cent in the nutritious 
qualities is generally sustained, while at the same time the 
moisture is by no means reduced, and consequently carriage 
still remains impracticable. 

It has long been endeavored to overcome these disadvan- 
tages by removing the surplus moisture by air-drying the by- 
products, so as to allow of storing and transporting them, and 
at the same time realizing their full market value. The result 
of such endeavors has been the construction of different kinds 
of air-drying machines, which has certainly been a step in the 
right direction, inasmuch as drying is undoubtedly the surest 
and safest way of preserving perishable substances. The 
removal of the water overcomes at once the two great obstacles 
previously encountered. The rapid decomposition ceases, and 
carriage to a distance becomes practicable, and the reduction 
in weight is very considerable. The consequence is that by- 
products, so dried, bring their full market value. 

The process of air drying has been no easy task on account 
of the low temperature required, wherever it is wished that 
the dried substance should retain its chemical composition 
unchanged, which in any article of food is a most important 
point for enabling a profitable result to be obtained. In gen- 
eral two drawbacks have rendered themselves conspicuous in 
connection with the air-drying machines hitherto in use; 
either, in order to shorten the drying process as much as 
possible, and to make it sufficiently economical, too great a 
heat has been employed, with the unavoidable result of seri- 
ously deteriorating the nutritious qualities of the material ; or 
else, when a longer time and a lower temperature have been 



AIR PRESSURES BELOW ATMOSPHERIC PRESSURE. /I 

employed for drying, the capacity of the ordinary drying 
machines has been so small that the working expenses have 
rendered the process unsuccessful commercially. 

All the foregoing disadvantages are avoided if the boiling- 
point of water is lowered, that is, if the evaporation is carried 
out under a vacuum. This plan is widely known and used for 
liquids, but not so much so for solid substances. For the latter 
it has first been successfully applied in practice by the vacuum- 
drying apparatus, which is designed to evaporate large quanti- 
ties of water contained in solid substances, in as short a time 
and at as low a temperature and expense as possible. 

This vacuum plan of drying is already in use for various 
solid substances, and the result has in every case been remark- 
ably satisfactory. Wet grains from a brewery or distillery, 
containing from 75 to 78 per cent of water, have by this drying 
process been converted in some localities from a worthless 
incumbrance into a food-stuff highly valued and sought after. 
The water is removed by evaporation only, no previous mechan- 
ical pressing being resorted to ; hence absolutely the whole of 
the solid matter is retained, of which, in any process of press- 
ing, a large proportion would have been carried off in a dis- 
solved state in the water. The result is a dry food stuff, rich 
in quality and satisfactory in appearance. 

From malt the removal of the moisture which it contains 
has to be effected very carefully, and required in the old-fash- 
ioned kilns as much as forty-eight hours, because the low tem- 
perature necessary could be secured only by slow combustion ; 
this method was and always is a risky one. In the first stages 
of the drying of malt the temperature has to be kept very low ; 
and in a vacuum apparatus, therefore, hot water, of which the 
temperature is easily regulated by a thermometer, may be 
used instead of steam as the heating agent at the outset, while 
at the same time as high a vacuum as possible is created in the 
drying cylinders by an air pump of special construction. 

If all the water were evaporated from the substances to be 



72 COMPRESSED AIR AND ITS APPLICATIONS. 

dried, the latter would of course be heated up to the same tem- 
perature as the heating surface, and would thereby be injured. 
This was one of the drawbacks connected with former plans of 
drying ; but it does not occur in the regular working of the 
vacuum apparatus, because such substances as beer grains or 
distillery grains, oats, barley, fruits, and vegetables, are never 
completely dried, but are always taken out of the apparatus 
while still retaining from 7 to 12 per cent of moisture. Even 
if they contained less, they would rapidly absorb again from 
the atmosphere such a quantity of moisture as their dry con- 
dition in the atmosphere allows. 

In the vacuum process, the boiling-point of the water con- 
tained in the wet material is brought down as low as 1 io° F. or 
43 C. ; the difference between this temperature and that of the 
heating surfaces is amply sufficient for obtaining good results 
from the employment of exhaust steam for heating all the 
surfaces of the vacuum cylinder. Under atmospheric pressure 
this difference of temperature would not exist; and to the same 
cause is also due the short time occupied in drying, notwith- 
standing the low temperature employed. The water contained 
in the solid substance to be dried evaporates as soon as the 
latter is heated to about no F., and as long as there is any 
moisture to be removed the solid substance is not heated above 
this temperature. The dried product, therefore, remains per- 
fectly unaltered in every respect, and is not in the least 
impaired in its chemical composition and nutritious properties 
by the drying process. 

THE VACUUM IN SALT-MAKING. 

The manufacture of salt by the vacuum process is becom- 
ing an important item in the industrial economy of the times, 
and is now carried on in Austria, England, and the United 
States. We illustrate, Fig. 19, the initial evaporating section 
of a triple effect system of Dr. S. Pick, of Szczakowa, Austria, 



AIR PRESSURES BELOW ATMOSPHERIC PRESSURE. 



which is in section of the first effect and almost self-explana- 
tory. The three pans are set side by side, as in a triple sugar 
apparatus, and the terminal connected with the condenser and 
air pump. 

The section shows the boiling chamber A (Fig. 19), the heat- 
ing chamber B, the collecting chamber C, and the filtering cham- 
ber D. The three sections are placed side by side a few feet 
apart, and are connected together by pipes as a triple effect. 
The heating chamber B of the first 
section is placed in communication 
with a steam boiler, or with the ex- 
haust steam from an engine, by 
means of the pipe E. The boiling 
chamber A of the first section is 
placed in communication with the 
heating chamber B of the second 
section by means of the pipe F, the 
second boiling chamber A 1 communi- 
cating in its turn with the heating 
chamber B 2 of the third section by 
the pipe F\ This latter section has 
its boiling chamber placed in com- 
munication with a jet condenser and 
air pump. G is the brine inlet pipe 
to the various sections and is in 
communication with the brine tanks, 

the brine being raised by vacuum and supplied automatically to 
the several sections. H is a pipe for automatically conducting 
the brine from the filtering chambers, D, to the boiling chamber 
of each section. J is a small pipe which connects the boiling 
chamber of the first and second sections with the condenser, and 
is used for assisting in maintaining a vacuum in each of those 
chambers. In like manner lis a small pipe for assisting the 
vacuum in the heating chambers of the second and third sec- 
tions by clearing them of surplus air (not shown in cut). 




Steam Trap 
Fig. 19.— vacuum salt pan. 



74 COMPRESSED AIR AND ITS APPLICATIONS. 

The boiling chamber of each section is simply an iron cylin- 
der, of larger diameter than the heating chamber beneath it. 
The object of the increased diameter is to enable the chamber 
to contain a large quantity of brine with a minimum of depth 
and a maximum of evaporating surface. The usual level of 
the brine is seen in the section, which is a sectional view of a 
single apparatus, the second and third sections not being 
shown. The heating chamber consists of a series of conical 
tubes of comparatively small diameter surrounding a central 
tube of larger diameter, as shown in the section. The whole 
of the tubes are inserted in a tube plate at top and bottom, and 
inclosed in a cylindrical chamber, into which steam is admitted 
in the first section by the pipe E, and after imparting its heat 
to the brine it is condensed, and passes away to a steam trap as 
shown. In the second and third sections the condensed water 
is drawn off by pumps. 

The reason for having the tubes conical is to prevent scal- 
ing, or, should scaling take place, that it may be easily 
removed, the larger diameter of the tubes being at the bottom. 

The settling chamber, immediately beneath the heating 
chamber, serves for collecting the salt as it is precipitated. It 
settles readily, as no movement takes place in the brine at that 
point. It is in direct communication with the upper or boiling 
chamber through the tubes of the heating chamber. This col- 
lecting chamber terminates in a sluice valve, and is in this way 
connected with the vacuum filter beneath it, which forms an 
important and essential feature of this system. Each filter con- 
sists of an upper fixed portion and a lower hinged portion, the 
filtering medium being attached to the lower portion of the 
filter at its junction with the upper part. The upper part is 
fitted with an air inlet cock and a water pipe, ending in a rose 
for washing the salt if necessary. The lower part of the filter 
is connected with the boiling chamber by a tube, the lower 
portion of which, as far up as the valve, is flexible, and yields 
when the filter is opened, as will be seen from the dotted lines. 



AIR PRESSURES BELOW ATMOSPHERIC PRESSURE. 75 

The method of operating this system is briefly as follows : 
Each of the three sections having been charged with brine to 
the proper level, which is that indicated in the boiling chamber 
A, steam is admitted to the heating chamber of the first section, 
in which the highest temperature is maintained. The brine in 
that section becomes quickly heated, and the steam given off 
from that brine enters the heating chamber of the second section, 
heating the brine in that section. The steam given off from 
the brine in the first section, after doing its work in the heating 
chamber of the second section, condenses and produces a 
vacuum in the boiling chamber of the first section, which 
vacuum is aided, if necessary, by opening the valve on the 
connection with the vaeuum pump. The pressure being 
reduced, the brine in the first chamber enters into violent 
ebullition at a comparatively low temperature. The same 
process is repeated in the second section, the steam chamber of 
the third section acting as a condenser, and producing a vacuum 
in the boiling chamber of the second section. The steam gen- 
erated in the third section is drawn off by the vacuum pump 
and condensed by the jet condenser, not shown. . It will be 
seen that the highest vacuum and the lowest temperature exist 
in the third section, while the highest temperature and the 
lowest vacuum occur in the first section. As the salt is pre- 
cipitated it settles in the collecting chamber, and at stated 
intervals the sluice valve is opened and the salt and brine are 
admitted into the filtering chamber. After settling there for a 
few seconds, the sluice valve is closed and the air cock on the 
filter is opened. The valve on the ascension pipe H is then 
opened, and in a few seconds more the whole of the brine in 
which the salt lies as in a bath is automatically transferred to 
the vacuum chamber, leaving the charge of salt resting on the 
filtering medium and perfectly free from brine. The valve on 
the ascension pipe is then closed, the filter opened, and the 
charge withdrawn. The filter is then closed ready for another 
charge of salt. 



j6 COMPRESSED AIR AND ITS APPLICATIONS. 

It will be observed that during the operation of letting 
down the charge of salt and withdrawing it from the vacuum 
filter, it is not necessary to stop working, the process of evapor- 
ation and production being thus rendered simultaneous and 
continuous, and, above all, automatic. The Miller system of 
salt-making is similar, only that a pipe leg is extended down 
from the cone to a tank seal with a hydrostatic height equal to a 
vacuum, and thus does away with the complication of the Pick 
system for the delivery of the salt. They are in operation in 
the salt works in Michigan. 

The multiple effect system of evaporation of liquids has so 
improved of late years that we illustrate in Fig. 20 one of the 
leading methods of evaporation by forcing the liquids through 
a tube system divided in small streams in contact with large 
heating areas, by which the liquid is not long subjected to 
heat, as in the process of boiling in large volumes. 

The illustration (Fig. 20) shows the Yaryan multiple effect 
in section, plan, and elevation. The operation is as follows: 
The steam, which may be either the exhaust from the engine 
or live steam direct from the boiler, is led into the cylindrical 
chamber surrounding the coils in the first effect. The liquid to 
be concentrated is fed into the first tube of the return bend 
coils of the first effect in a small but continuous stream, and 
immediately begins to boil violently, becoming a mass of spray, 
containing as it rushes along the heated tube a constantly 
increasing proportion of steam. The inlet end of the coil 
being closed to the atmosphere, and the steam being continually 
formed, the contents are propelled through the tubes at a high 
velocity, finally escaping from the last tube of the coil into the 
separator. Here the steam or vapor of evaporation, with its 
entrained liquid, which has been reduced in volume by the 
evaporation, is discharged with considerable force against the 
baffle plates, as shown in the figure at the upper left-hand 
corner, which separates the liquid from the steam, causing the 
former to fall to the bottom and permitting the latter to pass 



AIR PRESSURES BELOW ATMOSPHERIC PRESSURE. 



77 




78 COMPRESSED AIR AND ITS APPLICATIONS. 

off through an ingeniously contrived catch-all, which effectually 
removes any liquids still remaining into the chamber surround- 
ing the tubes in the second effect, where its heat produces the 
further evaporation of the liquid. In the second effect the 
liquid is led from the bottom of the separator of the first effect 
into the coils, and the same operation takes place as in the first 
effect, and so on through the entire system, whether triple, 
quadruple, or more effects are used, the volume of the liquid 
being constantly reduced in each effect. The steam from the 
final effect goes to the condenser and the vacuum pump, a high 
vacuum being thereby maintained in the separating chamber 
and consequently in the coils ; hence the boiling-point of the 
liquids is at a lower temperature than that of the surrounding 
steam, and by the condensation of the steam from the previous 
effect upon the cooler pipes in this effect a vacuum of a less 
degree is maintained in the next succeeding effect. This rela- 
tive reduction in pressure, and consequently boiling-temper- 
ature, automatically adjusts itself, however many effects are 
used, thus effecting the boiling of the liquid by the steam pro- 
duced by its own evaporation in the previous effect. In Fig. 
21 is shown a general view of this system of evaporation, with 
the final condenser and vacuum pump at the right-hand side. 

One of the advantages claimed for the system of evapora- 
tion of a liquid in the form of a spray subjected to heat under 
a vacuum is that it receives the heat quickly, and is concen- 
trated in the time of its passage through the tubes, and then 
relieved of its contact with the high temperature of the first 
effect and removed to a lower temperature with a higher 
vacuum, and so on through the whole number of effects. 

The spraying is produced by the admission of the liquid at 
pressure through a small orifice in a large tube, surrounded by 
the heating steam, evaporation commencing at once, and the 
steam of the evaporation, being unable to escape except by 
the path taken by the liquid, by its expansive force blows the 
small stream, already much broken up, into spray. 



AIR PRESSURES BELOW ATMOSPHERIC PRESSURE. 



79 




80 COMPRESSED AIR AND ITS APPLICATIONS. 

The rapid motion of the liquid through the tubes of the 
Yaryan system has the further advantages that, no single par- 
ticle remaining long in contact with the heated surfaces, in 
treatment of sugar and other solutions of a delicate nature 
injury from overheating is avoided, and the scouring action of 
the combined liquid and steam greatly reduces the liability to 
form scale. 

For the distillation of water for ice-making and for steamers 
at sea, this principle seems to be the most economical conserver 
of heat known. In the use of this system, with coal at New 
York prices, pure distilled water can be produced at a cost of 
fifty cents a thousand gallons, or less. To the manufacturer of 
ice any process which will give pure distilled water free from 
oil by use of the exhaust alone of the compressor is a desider- 
atum. Such a process does the Yaryan evaporator afford. The 
exhaust steam, instead of being condensed to produce the 
required distilled water, is used only to evaporate fresh water 
for distillation ; hence no trace of oil from the engine can be 
contained in the distilled water. The condensed exhaust is 
either used to feed the boilers or goes to waste. No elaborate 
system of filtering is required, and hence the ice is always clear 
and transparent. 

The address of the Yaryan Company is Times Building, New 
York City. 

In Fig. 22 is illustrated a detailed section of the Lillie sys- 
tem of evaporating and concentrating liquids and syrups. It is 
constructed for triple and quadruple effect by the Sugar Appar- 
atus Manufacturing Company, Philadelphia, Pa. It consists of 
a stack of slightly inclined evaporating tubes open into the 
steam chamber at the right and expanded in a thick tube plate, 
which separates the steam chamber from the evaporating 
chamber. The other ends of the tubes are closed save a 
minute air vent in the closed end of each, by which the tube is 
relieved of air. The liquid or cane-juice is circulated and 
spread over the tubes of the entire stack by a distributing tube 



AIR PRESSURES BELOW ATMOSPHERIC PRESSURE. 8 1 

over each vertical row of evaporating tubes, over which the 
liquid flows to the bottom, entering a receptacle or well, and 
into the suction pipe of a centrifugal circulating pump. 

The water of condensation in the evaporating tubes flows 
back and drops to the bottom of the steam chamber into a trap, 




Fig. 22.— lillie evaporator. 



and is carried to the next cooler effect, in which chamber it 
gives up a portion of its heat as vapor to assist in the evapora- 
tion of that effect. 

In the case of the multiple effect apparatus, the discharge 
from the bottom of the centrifugal pump is fed to the next 
effect, with the exception of the last effect, whose discharge 



82 



COMPRESSED AIR AND ITS APPLICATIONS. 



is the concentrated liquor, and goes to the final receptacle. 
Whether the system of evaporation consists of any number of 
effects from one to four, the train of operations are solely 
dependent upon the condenser and vacuum pump at the end of 
the train for the efficiency of the system. 

In Fig. 23 is illustrated a complete setting of the Lillie 
triple effect sugar train. 

In Fig. 24 is represented the elevation of a sugar pan work- 
ing on the dry system of evaporation, in which the water enter- 




FlG. 23.— THE LILL1E TKIPLE EFFECT. 



ing the condenser and the condensed steam, instead of passing 
through the air pump, passes down a stand-pipe or siphon by 
gravity to a cistern about 35 feet below the condenser, and 
which is thereby sealed against atmospheric pressure. In this 
system the air pumps are only required to keep the system 
relieved of air and a little moisture or uncondensed vapor. In 
this type of evaporator a series of copper coils, as shown, five 
in number, enter the evaporating pan from a header, shown on 
the outside, and circling around on the inside of the pan until 
sufficient surface is obtained for the work of evaporation, and 



AIR PRESSURES BELOW ATMOSPHERIC PRESSURE. 



83 



joining to another header, from which the water of condensa- 
tion from the heating steam is drawn off. In a multiple effect 
Fig. 24 represents the last pan, and Fig. 25 represents a quad- 




PlG. 24.— ELEVATION OF A SUGAR PAN. 

Joseph Oat & Sons, Philadelphia, Pa. 



ruple effect, in which the fifth pan shown in the cut is the 
finishing pan or last receptacle from which the syrup is drawn 
off to crystallize. Sometimes a surface condenser is used, in 
which a second pump draws off the water of condensation. 



84 COMPRESSED AIR AND ITS APPLICATIONS. 




FIG. 25.- QUADRUPLE EFFECT EVAPORATING APPARATUS. 
Joseph Oat & Sons, Philadelphia, Pa. 



AIR PRESSURES BELOW ATMOSPHERIC PRESSURE. 85 

THE SIPHON AND ITS WORK. 

The simple siphon for drawing liquids was known in many 
forms to the Egyptians generations before the Christian Era, 
and was much in use among the Romans, to whom was well 
known the part that a vacuum had in its operation, for it was 
then used for conveying a water-supply over elevations. The 
only improvement in modern times has been to supply means 
for discharging the air while the siphon is running. In Fig. 
26 A is the siphon, which can be operated over heights of 25 
and possibly 30 feet under very favorable conditions as to its 




-THE SIPHON. 



length. H and G are cocks to be closed when first filling the 
siphon ; B an air chamber, C a water seal for the cock below 
the air chamber, D a funnel for filling and also for sealing the 
upper cock against air leakage. 

The air that accumulates in the chamber B, by the opera- 
tion of the siphon, may be discharged by closing cock C, open- 
ing cock D, and filling the chamber with water. Close D- and 
open C, when any air below C will rise into the chamber, and 
water will take its place without stopping the running of the 
siphon. 

A PNEUMATIC VACUUM EXCAVATOR. 

During the construction of the Tay Bridge considerable 
difficulty was experienced in sinking the cylinders for the pier^, 
several expedients having been successively tried and aban- 



86 COMPRESSED AIR AND ITS APPLICATIONS. 

doned. At length Mr. Reeves, one of the engineers engaged 
on that great work, succeeded in devising an excavator on the 
pneumatic vacuum principle, by means of which the sand was 
sucked up from within the cylinders and discharged into hop- 
pers, the cylinders following down the displacement of the 
sand. One of these excavators, or sand pumps, as they are 
also called, has been completed by A. Wilson & Co., of the 
Vauxhall Iron Works, England, and has been inspected at 
work on their premises by a number of engineers. The 
excavator has been made for the New South Wales govern- 
ment, and will be sent to Sydney, N. S. W., where it will be 
used in sinking cylinders in connection with the improvements 
now in progress in the harbor there. The apparatus consists 
of a pair of cast-iron cylinders 4 feet in diameter, carried on a 
staging and placed in connection at their tops with an air 
pump driven by a small steam-engine. The connections are 
so arranged that the air can be exhausted either from one 
cylinder singly or both at the same time. The bottoms of the 
cylinders are connected with a suction tube 3^ inches in 
diameter, which leads down to the sand. Here again it is so 
arranged that the cylinders can be worked either singly or in 
combination by means of self-acting valves. The soil is dis- 
charged from each cylinder by a trap-door placed in its front. 
The engine and air pump are carried on the same framing, and 
the whole forms a very compact arrangement. In operation, 
the engine being started, the air is exhausted from one cylin- 
der ; the sand and soil rushing up into the vacuum thus created 
soon fill the cylinder, the fact being indicated by a tell-tale. 
The connection is then made between the air pump and the 
second cylinder, and that is similarly filled, during which time 
the contents of the first cylinder are discharged, and it is ready 
for the air pump by the time the second cylinder is full, and so 
the process continues alternately until the desired end has been 
attained. The excavator worked successfully ; a vacuum of 24 
inches was maintained during exhaustion, and the cylinders 



AIR PRESSURES BELOW ATMOSPHERIC PRESSURE. 87 

were rapidly filled with sand and water from a pit, the con- 
tents being quickly discharged. Besides the Tay Bridge, this 
excavator has been advantageously used at the Dundee Espla- 
nade, where a considerable quantity of land was reclaimed by its 
aid. It also succeeded in pumping the sand from a wreck at 
Fraserburgh, which led to the recovery of the vessel. In fact, 
the pneumatic excavator appears to have a wide field of prac- 
tical application before it. 



FLOW OF AIR INTO A VACUUM. 

The theoretical velocity of air flowing into a vacuum, if 
wholly unobstructed, is V2gh, or the square root of the sum of 
twice gravity multiplied by the height of the atmosphere of 
uniform density due to the height of the barometer, which at 
29.921 and 6o° F. is 27,816 feet in height and variable with the 
pressure of the barometer at any place. Twice gravity in 
middle latitudes is assigned as 64.344, but 64.32 is usually ap- 
plied to these computations. Then V64.32 X 27,816 = 1, 337.7, 
the velocity of the flow of the atmosphere into a vacuum in feet per 
second, at the above pressure and temperature. This velocity is 
claimed to be constant at all pressures, so that if a receiver be filled 
with compressed air at any great pressure, the velocity from an 
orifice into a vacuum would be the same during the time of dis- 
charge of the receiver from first to last, although the pressure 
would be decreasing by the escape of the compressed air. But 
the quantity of free air issuing per second would not be the 
same for different pressures in the receiver ; it will vary as the 
density at any moment, multiplied by the coefficient of the 
orifice. This uniformity of velocity of air flowing into a vacuum 
at all pressures does not hold when the discharge is made into 
the atmosphere. The height of the atmosphere, due to 1 

pound absolute air pressure, is — = 1,892.2 feet, and the 

14.7 
formula for the flow of air through orifices for differential 



88 COMPRESSED AIR AND ITS APPLICATIONS. 



pressures may then be used. V2g, h X c becomes V2g, h — h^Xc 
= velocity, in which h 1 = i ,892.2 for each absolute pound of back 
pressure in a partial vacuum chamber, and c a coefficient for 
the form of the orifice. For example, air at atmospheric 
pressure flowing into a chamber or tank at about half atmos- 
pheric pressure, or, say, 7 pounds absolute pressure, we have 
1,892.2 X 7 for the atmospheric height, and V2g. X ^13,245.4 = 
8.02 X 115.7 = 927.9, theoretical velocity, and 927.9 X c = .7 = 
649.5, the actual velocity in feet per second, .7 being the as- 
sumed coefficient for the orifice. 






Chapter V. 



THE FLOW 
OF AIR UNDER PRESSURE 
FROM ORIFICES 
INTO THE ATMOSPHERE 



THE FLOW OF AIR UNDER PRESSURE 
ORIFICES INTO THE ATMOSPHERE. 



FROM 



In the theoretical velocity for the discharge of air into the 
atmosphere under very low pressures, less than one-quarter of 
a pound per square inch, as measured by the pressure of water 
in inches of height, the variation due to difference in air 
density has been found so small that it has not been considered 
in the formula which was made the basis for computing Table 
X., as follows: Theoretical velocity = square root of pressure in 
inches of water X 66.1 ; which, multiplied by the coefficient C 
for a nozzle or a thin plate, gives the tabulated velocities. This 
table is based on the experiments of Daubuisson and computed 
for uniform density. The coefficients being for a nozzle of good 
form .93, and for an orifice in a thin plate .65. 

TABLE X. — Velocity of Air Under Low Pressure, in Inches of Water, 
with Equivalent Pressure in Pounds per Square Foot. Temperature, 
62 F. Barometer, 30 Inches. Theoretical and with Nozzle and 
Thin-Plate Orifice. (Box.) 



Inches 

of 
water 


Pounds 

pel- 
square 

foot. 


Theo- 
retical 
velocit3', 
feet per 
second. 


Nozzle 
.93 c. 


Thin 
plate 
.65 c. 


Inches 

of 
water. 


Pounds 

per 
square 

foot. 


Theo- 
retical 

velocity, 
feet per 
second. 


Nozzle 
• 93 c. 


Thin 
plate 
.65 c. 


0.01 


O.052 


6.61 


6.14 


4.29 


0.8 


4-15 


59-1 


54-9 


38.4 




02 


.104 


9-35 


8.69 


6.07 


•9 


4.67 


62.7 


58.3 


40.7 




04 


.208 


13-2 


12.3 


8.58 


1.0 


5.19 


66.1 


61.4 


42.9 




07 


•363 


17.4 


16.2 


li-3 


i-5 


7-79 


80.9 


75-2 


52.5 




1 


•519 


20.9 


19.4 


13.6 


2.0 


10.38 


93-5 


86.9 


60.7 




2 


I.038 


29-5 


27.4 


19.2 


2-5 


12.98 


104.0 


96.7 


67.6 




3 


1.558 


36.2 


33-6 


23-5 


3-0 


15.58 


114.0 


106.0 


74.I 




4 


2.077 


41.8 


38.8 


27.2 


3-5 


18.18 


124.0 


115.0 


80.6 




45 


2-337 


44-3 


41.2 


28.8 


4.0 


20.77 


132.0 


123.0 


85.8 




5 


2.597 


46.7 


43-4 


30.3 


4-5 


23-37 


140.0 


130.0 


91.0 




6 


3. Il6 


51-2 


47.6 


33-3 


5.o 


25-97 


148.0 


138.0 


96.2 




7 


3.635 


55-3 


51-4 


35-9 


6.0 


31.16 


162.0 


151. 


I05.3 



The coefficient for different forms of orifices and nozzles 
should be applied to the theoretical velocities in all cases. For 



9 2 



COMPRESSED AIR AND ITS APPLICATIONS. 



a sharp edge in a thin plate use the coefficient in the table, and 
with a plate with rounded orifice on the inside a coefficient of 
from .70 to .75 may be used according to the amount of curva- 
ture. With a clean cylindrical ajutage in length three times 
its diameter a coefficient of from .85 to .90 may be used, if the 
inner edge is slightly rounded. 

Fig. 27 approximates the best form of curve for short nozzles. 

The best form of curved taper nozzle will give a coefficient 

of .96, and a nozzle of the Venturi form, as illustrated in Fig. 

8, will still further the velocity to the 

theoretical figure or more. 

The velocity of air under the higher 
pressures discharging into the atmos- 
phere has been much the subject of ex- 
periment and discussion, and some of 
our mathematical authors have formu- 
lated complex equations that are not 
satisfactory in meeting reasonable results 
throughout the scale of pressures. We 
have adopted the theory of falling bodies 
and gravity as more applicable to the 
true conditions of the flow of air from 
orifices under pressure and into the atmosphere. For this pur- 
pose we use the height of an atmosphere of uniform density 
equal to the weight or pressure of the atmosphere at sea level 
with the barometer at 29.921 inches, or a pressure of 14.7 
pounds per square inch. 

Then the absolute pressure of a free atmosphere, 14.7 
pounds per square inch, divided by the assumed or receiver 
pressure in absolute atmospheres, which, multiplied by the 
height of the uniform atmosphere (27,816) and the product sub- 
tracted from the height (27,816), gives the proportion of the 
height to which the pressure is due, the square root of which, 
multiplied by the square root of twice gravity, equals the 
theoretical velocity in feet per second. 




-AIR JET NOZZLE. 



THE FLOW OF AIR UNDER PRESSURE FROM ORIFICES. 93 

For example, for a pressure of one atmosphere, or 14.7 pounds 



in receiver, the expression may be V2g x V 27,816 — — — or, 



educing, 8.02 x V — > an( i for two atmospheres, 8.02 x 



V 27,816 - 



For 50 pounds gauge: Pressure — 3. -\- 2l2. atmos. -4- ab- 

14.7 

solute atmosphere = — j_ -Alz = and 

4 14.7 4,405 



X 27,816 — = V2 1,500 X 8.02 = 1, 175 feet; 

4,405 

or by the decimal method, the ratio of the absolute pressures 

may be used, viz. : For 50 pounds pressure, 4-/ = .2272 and 

64.7 



V27,8i6 — (27,816 X .2272) = A/21, 496. 3 = 146.61 x 8.02 = 
1,175 feet theoretical velocity, as before. The theoretical 
velocity must be multiplied by the coefficient of the orifice for 
the actual velocity. The form of an air jet nozzle is of great 
importance for some uses to which the air jet is applied. If a 
sharp, quick-flowing jet is required, as used for cleansing and 
dusting, the inside should be smooth and curved from the butt 
to the tip, of which Fig. 27 represents the type of best form. 

For a longer nozzle of best form, the curves may take an 
elongated shape by extending their length with the same pro- 
portional lateral dimensions. 

By the experiments of Poncelet, Wantzel, and others, it was 
found that for pressures above the atmospheric pressure to y^-, 
yVj, \, i, 5, 10, and 100 atmospheres, the coefficient with a thin 
plate orifice became .65, .64, .57, .54, .45, .436, and .423 
respectively, and with a short tube .834, .82, .71, .67, .53, .51, 
and .487 respectively. 

There is a singular anomaly in the coefficients for a short 
pipe that does not correspond with the tabulated advance of 
the theoretical velocities, or of those from an orifice in a thin 



94 



COMPRESSED AIR AND ITS APPLICATIONS. 



plate, as derived from the experiments of Poncelet, Wantzel, 
St. Venant, and others, which show a maximum velocity from 
short pipes at a pressure of 50 atmospheres. 

From these considerations the following Table XI. of 
theoretical velocities, with coefficients and actual velocities from 
the orifices of thin plates and short pipes, has been computed : 



TABLE XL — Velocity of Compressed Air, Theoretical and from Orifices 
in a Thin Plate and from Short Pipes of a Length of Three Times 
their Diameters. The Coefficients of Contraction Decrease with 
the Increase in Pressure and are Derived from the Experiments of 
Poncelet and Others. 



Pressure 


Pressure, 


Pounds 


Theo- I 


?ifice in Thin 
Plate. 


Shori 


Pipe. 


retical 










atmos- 
pheres. 


inches of 


per square 


velocity, Coe 


ficient 


Actual 


Coefficient 


Actual 


mercurv. 


inch. 


feet per , 1 


of 


velocity. 


of 


velocity, 






second. cor 


trac- 


feet 


contrac- 


feet per 








t 


on. 


per second. 


tion. 


second 


O.OI 


0.3 


O.147 


94.4 O 


65 


61.4 


O.834 


87.7 


.066 


2.1 




246. 


643 


158. 


.825 


203. 


.10 


3- 


i-47 


299. 


64 


191. 


.820 


245. 


.136 


4.0S 




343. 


63 


219. 


.815 


283. 


.204 


6.12 




472. 


62 


293- 


•795 


375- 


.272 


8.16 




493- 


61 


301. 


•775 


3S2. 


• 340 


10.20 


5- 


552. 


59 


326. 


•755 


417- 


.408 


12.24 




604. 


58 


350. 


•733 


443- 


• 50 


15. 


7-35 


673. 


57 


334. 


.710 


47S. 


• 544 


16.32 




697. 


567 


395- 


.704 


491. 


.611 


18.34 




741. 


563 


417. 


• 694 


514. 


.680 


20.4 


10. 


780. 


56 


437- 


.686 


-35- 


.809 


24.2S 


12. 


855. 


55 


470. 


.678 


580. 


1. 


30- 


14.7 


946. 


54 


5ii. 


.670 


634- 


2. 


60. 


29.4 


1,094. 


50 


547- 


.600 


6-6. 


5- 


150. 


73-5 


1,219. 


45 


548. 


.540 


6sS. 


10. 


300. 


147- 


1.275. 


436 


556. 


.520 


663. 


20. 


600. 


294. 


1,304. 


432 


563. 


•507 


661. 


40. 


1,200. 


58S. 


1,323. 


428 


566. 


.498 


659- 


100. 


3,000. 


1,470. 


I.33L 


423 


563. 


.487 


648. 


200. 


6,000. 


2,940. 


i,334- 


418 


558. 


.476 


635- 



TABLE XII.— Flow of Air through an Orifice, in Cubic Feet of Free 
Air per Minute. Flowing from a Round Hole in Receiver into the 
Atmosphere. (William Cox.) 



Diameter 






Gauge Pressure. 






of 


























orifice. 


2 lbs. 


5 lbs. 


10 lbs. 


15 lbs. 


20 lbs. 


25 lbs. 


30 lbs. 


Inch. 
















1-64 


.038 


•0597 


.0842 


.103 


.119 


•133 


.156 


1-32 


•153 


.242 


•342 


.413 


.485 


•54 


■ 632 


I-16 


•647 


•965 


I.36 


I.67 


i-93 


2.16 


2.52 


% 


2-435 


3-86 


5-45 


6.65 


7-7 


8.6 


10. 


X 


9-74 


15.40 


21. S 


26.70 


30.8 


34-5 


40. 



THE FLOW OF AIR UNDER PRESSURE FROM ORIFICES. 
TABLE XII. {Continued). 



95 



Diameter 


Gauge Puessure. 


orifice. 


2 lbs. 


5 lbs. 


10 


lbs. 15 lbs. 


20 lbs. 25 lbs. 


30 lbs. 


Inch. 
















H 


21.95 


34-6o 


49 


60. 


69 


77- 


90. 


% 


39- 


61.60 


87 


107 




123 


138. 


161 




H 


6i. 


96.50 


136 


167 




193 


216. 


252 




U 


87.60 


133- 


196 


240 




277 


310. 


362 




% 


119.50 


189. 


267 


326 




378 


422. 


493 




i 


156. 


247. 


350 


427 




494 


55°- 


645 




iX 


; 2 4 2 - 


3S4. 


543 


665 




770 


S60. 


1,000 




I# 


1 35o. 


550. 


780 


960 










2 


625. 


985- 













Diameter 

of 

orifice. 



Inch. 
1-64 



Gauge Prkssure. 



35 lbs. 40 lbs. I 45 lbs. 50 lbs. 60 lbs. 70 lbs. 



• 173 


.19 


• 71 
2.80 


•77 

3-°7 


II. 2 


12.27 


44-7 


49.09 


100 


110.45 


179. 
280. 


I96-35 
306.80 


400. 
55°- 
7i5- 


441.79 
601.32 
785.40 



.26 
1.05 

16^8 
67. 
151- 



85, 

191 
340 

765 

1.004 



90 lbs. 100 lbs. 125 lbs 



.486 
1.97 
785 
31-4 
125. 



Chapter VI. 



THE POWER OF THE 
WIND 




THE POWER OF THE WIND. 

The power of the wind to lift bodies is well exemplified in 
the kite, and one of its most successful types is the box or Har- 
grave form, as illustrated in Fig. 28. The dimensions are 
given in the cut, the rear box being the same width as the for- 
ward one. The fore-and-aft sticks c, c may be made of tough 
pine or white wood f inch square ; the 
cross-pieces d, d, d, d, and the vertical 
pieces should be of the same width, 
but quite thin ; \ inch for the sides and 
■| inch for the cross-pieces. The 
diagonal braces e, e, e, e, should be of 
fine, strong fishline, twine, or, better, 
fine steel wire, for least resistance to 

Fig. 28.— the box kite. 

the wind ; all the corners should be 

tightly wound with fine strong twine and the fore-and-aft sec- 
tions covered with fine glazed muslin sewed to the frame. 

The bridle, a, b, should be double and 6 feet long, fastened 
to the fore-and-aft stick, at or near the rear side of the front 
section, and slightly adjustable for balancing the kite by trial. 

The bird form of kite, as used for centuries by the Chinese, 
failed to impress its self-sustaining principles upon the Western 
world until recent years, when tailless kites came into use and 
the box form became a useful aerial carrier of meteorological 
recording instruments. In the cut Fig. 28 is figured the 
dimensions of a 6-foot box kite, the lifting power of which for 
a 5 -degree angle with the horizontal course of the wind is about 
three-tenths of a pound per square foot of the surface of the top 
and bottom members, in a 3 5 -mile wind at the level of the kite, 
or for the 24 square feet about 7 pounds. The pull of the kite 
LofC. 



IOO COMPRESSED AIR AND ITS APPLICATIONS. 

may be considerable more for friction and the resistance of 
the frame. 

The first form of adjustable tailless kite was the keel kite, 
which is simply a diamond-shaped Eddy or Malay kite fitted 
with a fin or keel extending the entire length of the central stick. 
The width of the keel is about one-third of the greatest width 




FIG. 29. — HARGKAVE KITE. 



of the kite. The bridle is attached in the same manner as that 
of the Eddy kite, but the end secured to the tail of the kite is 
elastic, so that in a strong wind it stretches, allowing the kite 
to assume a smaller angle of incidence to the wind, the pressure 
of which upon the surface of the kite becomes relatively less. 
Kites of this pattern usually fly well, but are very liable to be- 
come distorted ; and when driven to one side by sudden shifts of 
wind, they recover their normal position less rapidly than other 
kites. The Hargrave kite is the most stable of those in use. 

The addition of the elastic bridle, previously tried on the 
Eddy and keel kites, effected a marked improvement. Usually 
the pull exerted upon the flying line by a rigid Hargrave kite 
without an elastic bridle is extremely variable and jerky, hence 
destructive alike to line and kite frame and to instruments 
carried by the kite. The elastic bridle allows the kite to yield 
slightly to gusty winds, and the records of instruments carried 
by the kites are as steady as are those made by instruments 
resting on the ground. This bridle has been modified and 
improved from time to time, and by its use the pull upon the 



THE POWER OF THE WIND. IOI 

line is under absolute control. The elastic may be adjusted so 
. that the pull never exceeds a certain maximum amount. The 
action of the bridle is shown in Fig. 29 and the method of 
adjusting in the two positions. The elastic portion of the 
bridle is shown at A, while B represents the rigid portion. 
In light winds the elastic alone receives the strain, as shown in 
the left-hand diagram, but in strong winds the elastic stretches 
until part of the strain comes on the rigid cord B, which is 
secured to the front of the kite. The angle of incidence is 
then very much less, and the effective pressure of the wind 
relatively diminished. 

In Fig. 30 is shown an adjustable bridle clip, made of light 
metal, with small rollers. The elastic portion of the bridle 
should be made strong enough to allow the kite to exert a pull 
of one pound per square foot of lifting surface, or sa3^ 24 
pounds for a kite of the dimensions of Fig. 28. These kites 
have been used in a 40 to 50 mile wind with safety when prop- 
erly constructed for the increased pressure. 

Much time has been spent in efforts to improve the efficiency 
of the kites. All the sticks, wires, etc., of which the frames 
are constructed are so shaped or ar- 
ranged as to offer the least possible re- 
sistance to the air, and the cloth covers 
are thinly coated with paraffine and 
ironed, so that a comparatively smooth 
and impervious surface is obtained. It 

r Fig. 30.— bhidle clip. 

was found that increasing the width of 

the rear cell of the kite caused it to fly at a higher angle; but 
since the pressure of the wind is much less on the rear than on 
the front cell, the increased weight rendered the kite less effec- 
tive in light winds. When the incidence of plane-surfaced 
kites is small, as it is when the elastic bridle is employed and the 
kite flown in high winds, the wind pressure upon the edges of 
the kite drive it backward and downward ; and while such kites 
fly safely in and are not injured by higher velocities, the angular 




102 COMPRESSED AIR AND ITS APPLICATIONS. 

altitude reached is so low that very little is gained in attempts 
to fly them in wind velocities exceeding 40 miles an hour. 

Experiments made to find the greatest efficiency of the box 
kite has shown considerable gain by curving the front edges of 
the supporting surfaces upward, as shown in the diagrams in 
Fig. 29. They should be made rigid by bent wood strips. 

Steel piano wire is used for the larger-sized kites (No. 14), 
which weighs about 15 pounds per mile, and should be wound 
on a strong hardwood drum. It will stand a working pull of 
100 pounds. With larger size kites, say of 50 square feet of 
lifting surface, meteorological recording instruments have been 
carried to a height of 12,000 feet. 



THE WINDMILL AND ITS WORK. 

The velocity and force of the wind for creating power was 
one among the earliest efforts of mankind for obtaining work 
from the elements of nature. 

Without going into details of the tedious progress and 
development of wind power through the slow march of 
improvement in windmill construction during the many cen- 
turies of their use as a prime mover, the final outcome for 
efficiency seems to have culminated of late years in the solid 
annular slatted form, as shown in Fig. 31, or the segmental 
slatted form, which reefs to the wind for regulating speed. 

The American type, or annular sail wind motor, which pre- 
vails all over Canada and the United States, is now being 
largely introduced into Europe, the Oriental and South Ameri- 
can countries. In this type, of which there are no less than 
twelve varieties, comprising a display of great ingenuity in the 
scheming of their gear, the sail surface is an annulus or broad 
ring, formed of radial slats. Each slat, of which there are, 
perhaps, fifty, is a small sail in itself, and is, in most cases, set 
in its frame at a fixed angle to the plane of motion, the effective 
wind pressure being automatically varied by making the wind 



THE POWER OF THE WIND. 103 

wheel slew out of, or away from, the wind, so that its disk 
becomes more and more oblique to the direction of the wind as 
the pressure increases, thus foreshortening the wheel to the 
wind. This form has a single vane or rudder parallel to the 
axis, and carried on an arm springing from one side of the gear 
frame. This rudder acts against the resistance of a weighted 
lever, which slews the wheel back into the wind again when 
the pressure subsides to the normal. This variety is called the 
"solid wind wheel," to distinguish it from those forms which 
have sail-reefing mechanism. Of the latter, one form in par- 
ticular, which seems to meet with most 
favor, merits description, if only on 
account of its curious and original 
reefing mechanism. 

In the type referred to, the annulus 
is made up of six, eight, or more seg- 
mental frames, each carrying a num- 
ber of fixed vanes and pivoted on axes 
which are tangential to a circle de- 
scribed on the wheel face. This wheel 
is reefed, both automatically and by 

hand, by causing the sail frames to turn on their axes, so that, 
when fully reefed, the frames assume a position parallel to the 
main axle, and are then quite ineffective, the mill being there- 
by stopped. Intermediate positions, of course, place the vane 
frames more or less obliquely to the wind by means of a large 
rudder in the wake of it. In some cases the reefing gear is 
actuated by a centrifugal governor. This mill, when seen at 
rest with the sails fully reefed, presents a very wreckish and 
generally startling appearance. It is strongly suggestive of a 
large umbrella which has had its ribs unshipped and has other- 
wise come to grief in a gale of wind. But it is a most efficient 
conserver of wind power. 

The velocity of the periphery of a windmill, constructed as 
in Fig. 31, should be from one and a half to twice the velocity 




HE MODERN W] 
MILL. 



io4 



COMPRESSED AIR AND ITS APPLICATIONS. 



of the wind for best effect, and to obtain this relation the angle 
of the slats at the periphery should be set at an angle of i8° 
from the plane of the wheel's motion, and at f of the radius of 
the mill the angle should be 34 , the slats having a gradual 
twist to meet the requirement of the angles. With about these 
angles the best mills are now built in sizes from 8^ to 30 feet 
in diameter. 

The actual power of these mills as taken from the shaft gear 
is : Area in square feet of the slats in the plane of revolution 
multiplied by the cube of the velocity of the wind in feet per 
second equals the horse-power. 

The average velocity of the wind in a large portion of the 
United States, and for the lowest force that will do effective 
work with a windmill, is 8 miles per hour for from 5,000 to 
6,000 hours in a year, and an average of 16 miles per hour may 
be expected for 3,000 hours per year; so that for a power that 
does not require daily attention and can be utilized for twenty- 
four hours of the day, it is the cheapest for all uses within its 
sphere of action. For pumping water for storage for all uses, 
there is no more economical prime mover. In the larger sizes, 
of 50 and 60 feet diameter, wind power is doing excellent work 
in our Western States for milling, and in all sizes is largely 
extending its usefulness in irrigation. The following table 
gives the sizes of windmills in common use, their power and 
capacity for pumping water with an average of a 16-mile wind 
for 8 -hours per day : 

TABLE XIIL— The Windmill and Its Work. 

















Diameter 


Horse- 






Irrigation 




Irrigation 


of mill. 


power from 


water 


15 feet high 


in acres, 


25 feet high 


in acres, 






pumped. 


per hour. 


column 4. 


per hour. 


column 6. 


%% feet. 


O.09 


O.04 


616 


O.18 


370 


0. 10 


10 " 


.16 


.12 


1,918 


•57 


1,151 


•339 


12 " 


• 25 


.21 


3,420 


1.02 


2,036 


.60 


14 


.40 


.28 


4-530 


i-37 


2,708 


.798 


16 


•50 


.41 


6,460 


1.84 


3,876 


1. 142 


18 


.70 


.61 


9.768 


2.83 


5,861 


I.727 


20 " 


I. 


•79 


12,465 


3-65 


7,479 


2.20 


25 


I.50 


i-34 


21,233 


6.27 


12,743 


3-75 


30 


3- 


2.25 


31,660 


12.88 


19,000 


7.61 



THE POWER OF THE WIND. 



105 



THE WINDMILL FOR ELECTRIC LIGHTING. 



One of the many useful applications of wind power is exem- 
plified in the adaptation of the windmill as a prime mover for 
the generation of electricity, and its storage for lighting and for 
power purposes at times 
when the wind is idle. 

In Fig. 32 is shown the 
arrangement for gearing 
and belting a windmill to a 
dynamo. 

The windmill-driven dy- 
namo charges a storage 
battery, which has an auto- 
matic cut-out when the mill 
runs too fast or too slow. 
The mill has also a regula- 
tor throwing it out of the 
direct course of the wind 
when running too fast, or 
for stopping the mill. 

A windmill 30 feet in 
diameter, equal to 3-horse- 
power in a 16-mile wind, 
running a dynamo, will 
generate current for 25 in- 
candescent lights of 16-candle power each. To run a plant 
of this kind successfully requires some means of obtaining 
current when there is no wind, or when the wind is not suffi- 
ciently strong for the power required. Some device for keeping 
the electrical pressure at the required figure should also be 
employed. For supplying current when the wind is light, or 
during a calm, it is customary to use a storage-battery. It has 
also been proposed to run a pump in connection with the wind- 




.— ELECTRICITY KRoM WIND POWER. 



106 COMPRESSED AIR AND ITS APPLICATIONS. 

mill and to store water in a tank, or convenient reservoir, 
using the water to run the dynamo by means of a turbine. 

To steady the electrical pressure when the dynamo is run 
directly from the windmill, as in the figure, three separate 
methods can be employed. A specially wound dynamo, giving 
a constant pressure over a wide range of armature speeds, is 
belted directly to the countershaft ; an ordinary dynamo is 
driven by a pair of cone pulleys placed between it and the 
countershaft, a governor on the pulleys regulating the speed 
ratio between the countershaft and the armature ; or an auto- 
matic regulator is arranged to place storage-cells in circuit with 
the dynamo as the speed falls, and cut them out as the speed 
rises. 

At times of the day or week when such a mill is not used 
for the generation of electric current for storage or direct light- 
ing, it will also supply through a pump the water required for 
a large country house. For the purpose of irrigation alone the 
windmill is of the greatest advantage to the agricultural inter- 
ests of the United States, and even in our Eastern States, where 
irrigation has been heretofore almost totally neglected, it 
has been found by trials that by the use of a windmill with a 
small storage capacity for water to meet contingencies the 
increase in a garden or small-fruit crop alone will amply pay 
the interest on the plant, and in seasons of severe drought the 
saving will pay for the plant. These are serious matters for 
consideration and for the success of our gardeners and small- 
fruit raisers. Recently a windmill has been erected in Ham- 
burg, Germany, 40 feet in diameter, which furnishes 120 
amperes at 160 volts, to charge accumulators for lighting and 
the operation of small motors. The automatic regulation to 
meet all contingencies of the wind having been made complete, 
this system of generating electric power seems assured of 
success. 






THE POWER OF THE WIND. 



107 



AIR COMPRESSION UNDER LOW PRESSURE. 




Fig. 33.— rotary blowei 



Beyond the power of the ordinary bellows and centrifugal 
rotary blower, the use of air under slightly higher pressure is 
often desirable, and for this purpose 
the double rotary blower is a most 
useful device for obtaining pres- 
sures up to 3 pounds per square 
inch. Fig. 33 is the form of the 
Root blower, in which the extended 
surface of the periphery of the 
wheels allows them to run loosely 

in the shell without friction, and with very small loss by air 
leakage. 

This class of blowers, unlike the ordinary fan, can be run 
at any desired low speed, and its pressure is positive for any 
measured volume of air under 3 pounds per square inch. 
Another form of light-pressure air compressor is the compound 
fan blowers of the Clarke and Hodges type. The one shown 
in Fig. 34 is a double blower with triple effect. The air is 
drawn in at each side of the blower and thrown out at increas- 
ing pressure successively by the fans on each side, and returned 
successively by the stationary parti- 
tions, with a final discharge at the 
central annular chamber. With these 
blowers a pressure of from 6 to 9 
pounds per square inch is obtained. 

One of the curious properties of air 
issuing from a bell-shaped nozzle of an 
air pipe, as illustrated in Fig. 35, is to 
hold a light ball close to the bell, allowing no more area between 
the ball and the bell than the area of the smallest diameter of the 
nozzle. The same effect is also shown with a light flat disk 
laid on another disk, with an orifice through which air is 




TRIPLE BLOWEE 



io8 



COMPRESSED AIR AND ITS APPLICATIONS. 





-AIR NOZZLE. 



36.— G A SOLI N E 
TORCH. 



blown. Much theorizing has been given to this phenomenal 
action ; but we believe it may be plainly seen that the expand- 
ing air in both cases produces a reflex or coun- 
ter movement of the outside air that neutral- 
izes the pressure beneath 
the ball and plate. 

The atomizing power of 

air under the low pressure 

of a fan or a foot bellows 

is a most useful appliance 

in laundries, and there are 

many examples of the use 

of air for atomizing fluids 

in medical and surgical use 

and the toilet. The spraying of colors on pottery and coloring 

dressing material on textile goods is a matter of economy in 

their manufacture. 

Air under low pressure, as derived from the operation of a 
simple hand pump, is much in use for torch-lights, and by 
plumbers for melting solder, and by braziers. 

The bicycle and vehicle tire pump is too well known to 
need special description. 

The air and gasoline torch, so much used in out-door illu- 
mination in street and construction work, is shown in Fig. 36, 

and consists of a tank into 
which a hand-pump is in- 
serted, drawing air from the 
open top through the piston 
and discharging it beneath 
the gasoline, producing a 
saturated air and vapor gas, 
which is carried to the 
Bunsen burner through the vertical pipe. The additional air 
for combustion is regulated at the burner, and the vapor at the 
valve in the pipe near the tank. A gauge shows the pressure. 




Fig. 37.— gasoline soldering copper. 



THE POWER OF THE WIND. 



IO9 




38. — AIR GAS 
BRAZIER. 



A small charge of gasoline, say, one pint to one gallon tank, 
gives best effect, and is safe for all this class of air-gas appara- 
tus. A similar apparatus, Fig. 37, is used for 
heating soldering coppers made hollow and 
with a side vent in the copper tip for relieving 
the flame. The pump forms the handle of the 
apparatus, so that the copper can be used on 
the torch apparatus for special work in the 
open air. It is much in use for making elec- 
tric wire connections. 

The use of air and gasoline vapor for braz- 
ing is much in use for small work, and is one 
of the most convenient means for brazing 
bicycle parts. In Fig. 38 is illustrated a 
double-flame brazing apparatus with external 
air pump and gauge. The handles at the back of the burners 
regulate the flow of the air-vapor to the Bunsen burners, and 
a fire-brick or graphite slab forms a back on which the flame 
impinges and is intensified. 

In the four-flame brazier (Fig. 39 ) the flames impinge on each 

other, enabling the work to be brazed subject to heat on all sides. 

Any desired pressure may be stored in the tanks within a 

safe factor of 

strength and the 

capacity of the 

hand pump; but 

the flame pressure 

must be regulated 

by the valves for 

best effect. In 

this connection a 

very simple and fig. 4 o. 

efficient jet com- 
pressor may be made for home work in brazing, glass-blowing, 
etc., with a small apparatus, as shown in Fig. 40, in which a 



i^rjjprct 





Fig. 39.— four-flame 
zier. 



IIO COMPRESSED AIR AND ITS APPLICATIONS. 

jet of water from a nozzle falling through the tube C draws in 
air through a side tube and forces it into the air chamber, 
where the water and air separate under pressure. The water 
is siphoned off through the water seal at a height due to the 
required pressure and the force of the jet. 

AIR PRESSURE IN GOLD-MINING. 

The winnowing of gold-bearing sands for separating the 
sand and dirt from the particles of gold is in use, and many 
machines of various forms are in operation in the dry-placer 
gold-mining districts. An ordinary bellows furnishes an air 
blast, which separates the fine sand and dust 
from the gold on the riffle screens and blows 
the dust away. A gold winnowing machine 
is illustrated in Fig. 41. 

AIR PRESSURE FOR GRAIN AND VENTILATION. 

The winnowing and cleaning of grain is 
not new, and its aeration in bins and store- 
Fig. 4 i- - dry-placer houses is one of the modern economies for 

MINING MACHINE. . 

preserving gram from must, mildew, and 
heating. Air under the higher pressures is now used to ven- 
tilate grain bins 60 feet in height, and thus obviate the neces- 
sity of frequent transfer of the grain for its aeration. 

The motion of air for ventilation is so well known, and so 
ably treated in works on ventilation of buildings and mines, 
that we refer for this subject to such works, of which there are 
many published. 

COMPRESSED AIR FOR BLOWING GLASS. 

One of the later applications of compressed air, for the relief 
of oppressed humanity in regard to health and the elimination 
of disease caused by the artisan's work, is in the blowing of 
glass. 




m 



THE POWER OF THE WIND. I I I 

The operation of blowing is hard on the workman, not only 
because of the muscular effort that it imposes on him, but also 
because of the great volume of air that he has to draw into his 
lungs within a very short space of time. Such defective con- 
ditions are further aggravated by the high temperature and dry 
atmosphere of the place in which he has to move, and this 
makes him liable to special affections, such as ulceration of the 
lips; deglutination and distention of the cheeks, leading to the 
formation of nacreous patches — an indication of an alteration in 
the mucous membrane ; fistulas of the salivary canal ; and a 
predisposition to emphysema and hernia. 

As the blowing is very often performed by young children 
during their development, the results are still more disastrous. 

In order to overcome these inconveniences, a series of 
apparatus has been invented with a view to securing a substi- 
tute for blowing by mouth. 

The difficulty in applying blowing apparatus to the glass- 
worker's tube resides in the fact that the workman is obliged 
to rotate the latter continuously in order to keep the piece of 
glass that is being worked in an axis that is sensibly the same 
as that of the tool that supports it. The position of this tube 
varies according to the kind of work being done ; so, in order 
to satisfy such different conditions, there have been constructed 
three types of apparatus to be used: (i) According as the work- 
man is making the glass by revolving it according to a hori- 
zontal axis ; (2) revolving it according to a vertical axis, the 
glass being under the tube ; or (3) revolving it according to a 
vertical axis, the glass being above the tube. 

This apparatus, moreover, is based upon the use of an air 
pipe, into which the workman fits his tube, and of an auto- 
matically closing cock that he actuates either with his hand or 
with his foot through the intermedium of levers, so as to pro- 
duce the expansion that he requires. 

For the blowing of glass that is to be rolled a leather pipe 
is applied to the blowing tube by the boy who helps the work- 



112 COMPRESSED AIR AND ITS APPLICATIONS. 

man ; such is the case in the manufacture of tubes and of 
cylinders for window glass. In this case the compressed air is 
distributed on an inclined plane, over which descend the dis- 
tributing pipes. 

The advantages derived from the use of compressed air 
are of several kinds : It permits, in the manufacture of drink- 
ing glasses, to do away entirely with blowing by the mouths 
of children, and, with very rare exceptions (mostly through 
inattention of the workman), with blowing by the mouths of 
adults. 

It protects the latter, then, against the special affections that 
were brought on by the old method of blowing. There being 
less fatigue for the workman, he produces better work and a 
greater quantity of it, and the articles are manufactured with 
greater precision. Finally, the use of this process permits of 
obtaining, without fatigue to the men, articles of dimensions 
that have been hitherto unknown, both as regards bulk and 
other dimensions, such as length and thickness. The limits 
that may be reached are governed only by the weight of the 
material operated upon. This process, moreover, is very 
elastic, since, in consequence of the successive expansions that 
the workman produces at will, the pressure may ascend from 
less than an ounce per square inch to several pounds' pressure. 
In air-pressing glass in moulds it is a great relief to the strain 
on the lungs, and makes better work, due to greater control of 
the pressure. 



Chapter VII. 



ISOTHERMAL COMPRESSION 

AND 

EXPANSION OF AIR 



ISOTHERMAL COMPRESSION AND EXPANSION OF 

AIR. 

The free air of the atmosphere in its natural condition may 
be considered, in all ordinary computations for its use by com- 
pression or expansion, as a perfect gas, although there are 
small differences of effect due to moisture, which modifies the 
density of air under the process of compression and expansion, 
and at a certain degree of compression seems to squeeze out, as 
we may say, the excess of vapor upon cooling to normal tem- 
perature in the form of water of condensation. The vapor of 
water in air that can be held under the various degrees of com- 
pression and expansion acts like the properties of air, but is of 
itself lighter than the other constituents, and contributes to the 
atmosphere the weight or gravity in proportion to its amount 
of saturation. Like air itself, and each of its constituents of 
the so-called permanent gases, moisture is liquefied by pressure 
and the lowering of temperature. 

Dry air being a mixture of several gases, which at ordinary 
pressures and temperatures are so far from their liquefying 
point that they are called permanent gases, may, for all prac- 
tical purposes, be considered as a perfect gas, and be said to 
obey the same laws. Any gas near its liquefying point is called 
a vapor, and we may then say that the difference between vapor 
and gas is one of condition only rather than of composition. 

Without entering upon the subject of the molecular consti- 
tution of air and its component gases, which has been thor- 
oughly treated in the able works of Carnot, Clausius, Maxwell, 
Tyndall, and others, we will first consider the primary law of 
gases, which relates to the isothermal compression and expansion 
of air. 



n6 



COMPRESSED AIR AND ITS APPLICATIONS. 



This law of the compression and expansion of air and of 
other gases without change of temperature was first formulated 
by Boyle, in England, in 1662, and was further established 
by Mariotte, in France, in 1674. It is called Boyle's law, and 
relates to the isothermal compression and expansion of air and 
other gases, and was written: " When the temperature is kept 
constant, the volume of a given gas varies inversely as its pressure 
or elastic force ; that is to say, the product of pressure and volume is 
constant." 

This has been since found not absolutely true, for in 
Regnault's experiments in 1847, with a better apparatus, it 




Fig. 42.— isothermal diagram. 



was found that the product of volume and pressure at atmos- 
pheric pressure 14.7 (V , P„), divided by the product of volume 
and pressure at a higher pressure (V,, P,), resulted in a slightly 
increased volume, which was due to the difference in pressure 
at constant temperature. This amount was very small, and 
increasing to but .0063 of the volume at 13 atmospheres, so 
that for all ordinary computations Boyle and Mariotte's law 
represents the practical requirements of isothermal compression 
and expansion. According to this law, the product of the 
volume (V) and pressure (P) of air or a gas is always a constant 
quantity at the same temperature — that is to say, if you reduce 



ISOTHERMAL COMPRESSION AND EXPANSION OF AIR. I 1 7 

a given volume of air to half its bulk by external pressure, 
without change of temperature, then the pressure will be 
doubled, and by inverting the operation and expanding a given 
volume to twice its bulk, by external work, without change of 
temperature, the pressure will be reduced one-half. 

A graphic diagram of the pressure curve, due to isothermal 
compression, may be readily obtained from the algebraic ex- 
pression of Boyle's law of the product of the pressure and 
volume. Then PV= Constant. 

Let P = the initial pressure of one atmosphere = 14.7 
pounds per square inch, and P„ P„, P 3 , P 4 , the vertical ordi- 
nates of the diagram (Fig. 42) representing the fractional parts 
of compression, or the position of a piston at different points in 
its traverse of the cylinder, which = 1. 

Let P O represent a vertical space equal to one atmosphere 
(14.7), and each of the five spaces above equal to P O, and 
number them 1, 2, 3, 4, 5. 6 atmospheres. Then the areas 
contained in the rectangles P, 1— P lf 2 — P„, 3 — P 3 , 4 — P 4 , 5— P 5 , 
6, will be equal to one another, and a curve meeting the points 
of intersection of the vertical and horizontal ordinates is that of 
a hyperbola, one of the properties of which is, that the area 
of the rectangle contained by the horizontal and vertical ordi- 
nates from their points of intersection are the same, or equal 
in area. 

Then for any value of the volume V as at a half-stroke of 
the piston, the pressure P is represented by an inversion of the 
fraction of the stroke f-, and for two-thirds of a stroke the in- 
version of the reciprocal of the fraction, or -f-, represents the 
pressure in atmospheres from the absolute zero of pressure, 
which for gauge pressure requires the atmospheric pressure 
(14.7) to be deducted. Hence, the inverted reciprocal of any 
fraction of the travel of the piston in isothermal compression 
indicates the absolute pressure. 

Then for obtaining the proportional part of the stroke of a 
piston from the terminal, for any desired gauge pressure, divide 



Il8 COMPRESSED AIR AND ITS APPLICATIONS. 

the absolute or atmospheric pressure (14.7) by the absolute 

p 
pressure, plus the gauge pressure, - — — = D, the distance of 

the piston from the terminal. 

For example: at 75 pounds of gauge pressure, isothermally, 

the piston would be at liZ — = .1638 of its stroke from the 

14-7 + 75 

terminal, and this amount will also represent the volume of 
delivery in parts of the whole stroke, neglecting the clearance 
space. 

In this manner the values in column 5 in Table XVII. were 
computed, which also shows the relative volumes of com- 
pressed air to free air for any pressure from 1 to 3,000 pounds 
at the normal temperature of 6o° F. 

In column 3 of Table XVII. is shown the volume of free air 
to one volume of compressed air at the gauge pressures in 
column 1, and is computed by dividing 100 by column 7 in 
Table XVI., or by dividing 1 by column 5 in Table XVI. In 
column 7, Table XVII., is shown the mean isothermal pressure 
per full piston stroke, neglecting the clearance, which of itself 
will slightly lessen the mean pressure. 

T —1— 14 

This was computed by the formula p X — d~~ — P = mean 

pressure, in which p = absolute pressure, or the acquired gauge 
pressure -4- normal pressure (14.7). R = the ratio of the 
absolute pressure divided by the normal pressure, and H the 
hyperbolic logarithm of the ratio R : P = the normal pressure 

(I47). 

Then, for example, the mean pressure for isothermal com- 
pression to 100 pounds gauge pressure will be 1 14.7 X 

7.8027 

-14.7 = 30.193. Ratio R = II4 ' 7 — 7.8027, the logarithm of 

14.7 

which will be found in a table of hyperbolic logarithms, or the 

common logarithm multiplied by 2.302585. 



Chapter VIII. 



THERMODYNAMICS 



THERMODYNAMICS. 

Heat for a long time was supposed to be a special sub- 
stance more or less contained in air, the gases, and other sub- 
stances, which could be taken up or intensified by compression 
or squeezed out of a body, as air or gas, and the tempera- 
ture of a body was thought to depend upon the amount of the 
heat substance present in it. The phenomenon appeared ra- 
tional, but later investigations pointed to the vibratory molec- 
ular theory as being the correct solution of the mystery. 

The fact that heat did not increase the weight of bodies was 
a stumbling-block, and many ingenious theories were adduced 
to get over the objectionable features of the early theories, yet 
none proved satisfactory. The relation of heat to and its effect 
upon the properties of air and its constituents is undoubtedly 
no longer a generic hypothesis, and whether it be molecular 
vibration or some other form of energy, it is a fact in regard 
to its influence and power for changing the condition and con- 
stitution of matter. Then heat is a form of energy, free from 
ponderability and possessing the power of entrance into all 
substances, and by its action it produces work through the 
expansion of the substance in which it acts, by virtue of such 
expansion and the pressure and motion induced thereby. 

The accepted law in regard to the expansion and contraction 
of air and other gases by changes in temperature, or their 
condition in relation to the absorption and elimination of heat, 
was formulated by Gay Lussac in France, and Charles in 
England. 

It is called Gay Lussac s Law, or the second law of perfect 
gases, it being understood that a perfect gas is a condition in 
which the increments of expansion and contraction are exactly 



122 COMPRESSED AIR AND ITS APPLICATIONS. 

equal throughout the whole range of operation for both volume 
and temperature. This is not strictly true with any of the 
so-called permanent gases, for it is now found that all gases 
are only the vapors of liquids, having a vastly lower tempera- 
ture degree of liquefaction and refrigeration than water. 

With air the law is so nearly true that for all engineering 
purposes it is accepted in ordinary computation. 

Without delving into the relation of heat to other bodies 
than air and its constituents, we need only formulate the rela- 
tion of heat to the expansion and contraction of air as composed 
of its constituents, nitrogen, oxygen, argon, carbon dioxid, and 
their contained vapor of water. 

Heat becomes a means of compression with air when its 
volume is kept at a constant measure ; and heat is made mani- 
fest by increase of temperature when a measured volume of air 
is reduced by external pressure. The terms of both conditions 
are of equal value : the heat of compression and the cold of 
expansion are positive and negative equivalents from any 
initial temperature. 

The pressure of air or any of its component gases is exerted 
in direct proportion to its variation in density, and both 
pressure and density vary inversely as the volume, supposing 
the temperature to be kept constant. 

At constant volume the density varies as the pressure and 
also varies as the absolute temperature. 

Heat as a mechanical quantity has a measure, which is 
gauged by its effect in raising one pound of water at its maxi- 
mum density, through one degree of temperature by the 
Fahrenheit scale. It is called the British thermal unit to dis- 
tinguish it from the French caloric, which is the quantity of 
heat required to raise i kilogramme of water at its maximum 
density, through one degree Centigrade. 

Heat and mechanical energy are mutually convertible, and 
are measured in foot-pounds of power per heat unit, and this 
relation is termed the First Law of Thermodynamics.. The exact 



THERMODYNAMICS. 123 

value of its measurement from experiments of Dr. Joule, in 
England, and of Professor Rowland, in the United States, va- 
ries slightly at various temperatures, and as measured by the air 
or mercurial thermometer, the extremes of which are from 772 
to 784 foot-pounds per British thermal unit. The number 778 
is probably nearly correct, and will be used in this work. This 
value is sanctioned by good authority, and, although not Dr. 
Joule's figures, it is termed Joule 's equivalent and designated as 
a mathematical factor by the letter J. 

SPECIFIC HEAT OF AIR. 

The specific heat of air at constant pressure varies very 
slightly with the variation of the air temperature ranges in 
which the experimental data were obtained. The assignment of 
the average amount of heat required to raise one pound of air 
through one degree of temperature was found by Regnault to 
be 0.2375 of a thermal unit, within the range of temperatures 
in practical use, from 32 to 328 F. 

This is accepted as the specific heat of air at constant pressure 
(cp) during which the volume was enlarged during the absorp- 
tion of heat. 

The specific heat of air at constant volume has not been 
found accurately by direct experiment, but has been deduced 
from the work produced by the expansion of a given volume by 
the air value of one thermal unit (.2375) at constant pressure. 
This was found by Joule to be equal to .0686 of a thermal unit, 
and .2375 — .0686= .1689, the accepted value of the specific 
heat of air at constant volume (cv) . 

Then using the mechanical equivalent for one thermal unit 
as a basis (778), the mechanical equivalent for air will be in 
proportion to its specific heat; then 778 X .2375 = 184.77, the 
mechanical equivalent of one pound of air at constant pressure 
(Mcp) and 778 X .1689= l 3 l -&> "the mechanical equivalent of 
one pound of air at constant volume (Mcv). 



124 COMPRESSED AIR AND ITS APPLICATIONS. 

The weight of one cubic foot of dry air at sea level, barom- 



12.387 



.080728 



eter 29.921 and 32 F., is 0.080728 lb., and 

cubic feet in one pound of air at 32 F. 

Then the total pressure of the air at sea level per square foot 
(P ) 21 16.2, multiplied by the volume of 1 lb. (v o ) 12.387 c. ft., and 
divided by the absolute temperature from 32 F., 492.66, equals 
the difference in the specific heats of air in foot-pounds at con- 



stant pressure and at constant volume, viz. 



2 1 16.2 X 12.387 



53-17- 



492.66 

Then, as above stated, the mechanical equivalent of one thermal 
unit per pound of air at constant pressure (Mcp) = 184.77 ft- lbs. 

and at constant volume (Mcv) = 13 1.60 " 

Difference Mcp — Mpv = (D) = 53.17 
53.17 as a ratio will be noted and used in some of the formulas 
further on. 

The specific heat of air has been found by experiments of 
Professor Linde not only to increase by its temperature den- 
sity, but also to increase by density from compression. He 
has computed an interesting table of these values, which we 
here reproduce : 

TABLE XIV. — Specific Heat of Air at Various Temperatures and 
Pressures. 



Temperature, 
Fahrenheit. 


Pressure in Atmospheres and Pounhs. 


14.7 lbs. 


10 
147 lbs. 


20 
294 lbs. 


40 
588 lbs. 


70 
1029 lbs. 


100 
1470 lbs. 


212° 

32 

-53 

-148 

— 238 

-274 


.2372 
•2375 
.2380 
.2389 
.2424 
.2467 


.2389 
.2419 
• 2455 
.2585 
•3105 
.4147 


.2408 
.2465 
.2572 
.2844 
.5048 


.2446 
.2512 

.2785 
•3697 


.2512 
•2773 
•3319 
•3461 


.2583 
.2986 
.4124 



It is observed by inspection of the table that the specific 
heat of air at constant temperature increases with the pressure, 
at an increasing ratio at ordinary temperatures, and is over 25 
per cent at 32 from 1 to 100 atmospheres, the specific heat at 



THERMODYNAMICS. 125 

32 , .2375, being the term in use for air computations. It also 
increases largely with its density from increase of pressure with 
decrease of temperature, as well as with decrease of .tempera- 
ture at constant pressure. 

ABSOLUTE TEMPERATURE AND ITS ZERO. 

The recent experiments of scientists, and especially those 
who have been operating in the liquefaction of air and other 
gases, seem to have thrown some doubt upon what has hereto- 
fore been conceded as absolute zero, and the fact of an absolute 
zero has been lately ridiculed and stated to be a " thermody- 
namic heresy," and that the beautiful diagrams drawn from its 
equations or formulas are misleading. 

We take no stock in flimsy denials based on no better foun- 
dation than mental doubt. The operations of computation 
from the adopted facts and formulas work well within the 
scope of practical engineering, and it is safe to follow them 
until something better is found that is based upon an equally 
good foundation. 

So that it may be taken for granted that the zero of the scale 
of temperature by which the various computations in Aerody- 
namics are made is the lower terminal in the heat scale at which 
no further division can be made and no further expansion of 
air or gas can be obtained. It is the equivalent of absolute cold 
and of absolute vacuum. 

The lowest temperature that has as yet been reached experi- 
mentally is that of frozen liquid air at a temperature of — 404 
F. or only 56 above the computed absolute zero. 

In order to obtain the starting-point of the absolute scale, a 
backward process was made, based upon the expansion of air 
through a measured range of temperature between two fixed 
points that are well known and reliable in thermometric work. 

Regnault found that if a volume of air be kept constant at 
various initial pressures of from 2.12 pounds absolute to 70.7 



126 



IMPRESSED AIR AND ITS APPLICATIONS. 



pounds absolute, the volume when heated from 32 F. to 212 
F. expanded at the lowest initial pressure to 1.36482 and at 
the highest pressure to 1. 37091, a difference of .00609, which 
was attributed as due to some peculiar property of an imperfect 
# gas in its variable expansion under different 
pressures. It may have been from the in- 
fluence of moisture or the vapor of water so 
difficult to eliminate from air experiments, 
and here comes the basis of the so-called 
"thermodynamic heresies." 

At atmospheric pressure, however, the 
expansion from one volume was found to be 
1.3665 intermediate between the other deter- 
minations, and this rate was adopted for ob- 
taining the ratio of expansion and contraction 
per degree from the freezing-point of water 
(32 F.) and its boiling-point (212 F.). 
These three ratios seem to indicate a curve 
in the expansion line above and the contrac- 
tion line below the trial temperatures, which 
might extend the absolute zero far below the 
limit as computed from the mean ratio ; but 
as this has not been fully shown experi- 
mentally, the adopted ratio seems to answer 
all practical purposes within the ordinary limits of engineering 
work. 

By dividing the ratio of expansion by the number of degrees 
over which it extended, the ratio for each degree was obtained, 




_.L±L 4SQ./3 Ab. Zero 



Fig. 43.— scale of ab 
solute zero. 



•3665 

180 



.00203611 = the expansion of air by volume for 



rise in temperature ; therefore 



491.13, which 



.0020361 1 

represents the number of degrees equivalent to the volume (1) 
from which the departure for expansion from absolute zero was 
started ; it represents the number of degrees below the freezing- 



THERMODYNAMICS. 12J 

point (32° F.) at which air ceases to be divisible either in ex- 
pansion or in temperature; and 491. 13 — 32 = 459. 13 below 
zero F. was adopted for the absolute zero for a perfect gas. 
This value has been much used, but by later experiments of 
Joule and Thompson, and probably owing to a small variation 
in the relative value of air expansion throughout the scale of 
experiment, the absolute zero has been fixed and accepted by 
good authorities at 492. 66° below the melting-point of ice 
(32 F.) and at 460. 66° below zero F., and will be so used in 
this work. 

This assignment of the absolute zero (492.66) makes a slight 
variation of the ratios used for the computation in the older 
tables of air compression and expansion, which will then be- 

0.00202978 per degree Fahr. for extreme .tem- 



492.66 

peratures ; but this need not change the ratios as actually found 
between 32 and 212 F. (0.0020361 1) for any range of temper- 
ature in ordinary use ; except that the expansion of air by heat 
at very high temperatures may not follow the ratio exactly. 

The indications are that there appears to be a slight curve 
in the expansion line from 32 F. to the absolute zero, which 
when extended from 212 upward may slightly increase the 
volume at high temperatures as computed by the ratio. 

It ma3' be asked whether it is possible that air or gas when 
deprived of all sensible heat will cease to occupy space? We 
answer no! For at this time it is well known that all gases and 
their compounds, as air, are but vapors of liquids, that liquefy 
and become frozen into solids before the temperature of abso- 
lute zero is reached. Then we must consider that the absolute 
zero of our ratio scale of atmospheric temperatures is the point 
of elimination of its values at its lowest degree. 

With the ratio of .0020361 1 as the increase per unit degree 
Fahr. the volume and pressure may be computed for various 
temperatures for the expansion of the volume of one pound of 
air expressed in cubic feet, and also for the pressure of a con- 



128 COMPRESSED AIR AND ITS APPLICATIONS. 

stant volume by change of temperature. In Table XV. are 
given the volume, pressure, and density of air at various press- 
ures from o to 3000 F. It nearly follows the ratio given above 
within a fraction. 

The expressions for the ratio R, for the inner work per- 
formed under atmospheric pressure, may be written 
V P V P V P 

~t~ ~t7 t7 

That is, if we divide the specific volumes, multiplied by their cor- 
responding pressures, by the corresponding absolute temperatures, 
the quotients are constant and equal to K or 53.17, for 32 ° F. and 

for the pressure per square inch the ratio will be 5j ' ' = 0.3696. 

144 

rru V. X p„ T> A V o X p„ T 1 R X T 

Then ° Fn = R, and ° r ° = T; also — _ — = p„, 
T R V Fo 

i R X T , r 

and — — — = V . 

Po 

For example, one pound of air at 32 F. = V or 12.387 

cubic feet, p = atmospheric pressure 14.7, and the absolute 

temperature at 32 is 492.6. 

12.387 X 14.7 , , o T3 -■ -. 12.387 X 14-7 

Then — -A^- = .369648 = Ratio, and ,^ Q / = 

492.6 .369648 

492.6, also - 369648X492-6 and -369648X492.6 ^ 

y 12.387 4/ ' 14.7 

12.387, following the equations as above written. 

In Table XV. the 1st column shows the degrees of tempera- 
ture from o° F. to 3000 F. The 2d column shows the volume 
of 1 pound of air at the different temperatures in the 1st col- 
umn. The increase in volume is obtained by multiplying the 
ratio .00203611 by the number of degrees above 32 and by the 
volume at 32 (12.387), and to the product add the volume 
12.387; so that, for example, for the expansion of air from 32 
to 340 we have a difference of 308 , and .00203611 X 308 X 
12.387 = 7.7681 -f- 12.387 = 20.155 cubic feet of air, equal to 1 
pound as found in the second column opposite 340 in the 1st 



THERMODYNAMICS. 



I2 9 



column. The small fractional difference arises from the cutting 
off of fractions in the terms of the computation. 

v X t 



By using the expression 



for the volume of one pound 



of air as expanded by heat, as in column 2, Table XV., the vol- 
ume v = 12.387 at 32 , and at 360 the absolute temperature is 
360° -f 460.6 = 820.6, and the absolute temperature below 32 is 

* rr-L t, 4.1, +.• 12.387 x 820.6 ,. : . 

492.6. Then, as by the equation, — — - = 20.63 cubic 

feet in the volume at 360 expanded by heat from 32 ° F., as 
given in column 2 opposite 360 in column 1. 

TABLE XV.— Volume, Pressure, and Density of Air at Various Tempera- 
tures. From Normal Volume and Pressure at 62 F. (Haswell.) 



of . 

3'S 


e 

nd of 

sric 
ds. 




of 

foot 
r at 
ures 
n 1. 


£ ® 





*5 °g- d 


of 

foot 
rat 
ires 
1 1. 


3 <U 


Il-lll 


2 O g <D +> 


bo3 u 3 


* § 


iliPJ 




If S|l 









|S||8 




"-n O IP c 

►^ <U m 2 |_, 

IS M 




p. 






Cube feet. 


Lbs. per sq. in 


Lbs. 




Cube feet. 


Lbs. per sq. in. 


Lbs. 


o° 


II.583 


I2.g6 


.086331 


360° 


20.630 


23.080 


.048476 


32 


12.387 


13.86 


.080728 


380 


21. 131 


23.640 


•047323 


40 


12.586 


14.08 


•079439 


400 


21.634 


24. 200 


.046223 


50 


12.840 


14.36 


.077884 


425 


22.262 


24.900 


.044920 


62 


I3-I4I 


14.70 


.076097 


450 


22.890 


25.610 


.043686 


70 


13-342 


14.92 


.074950 


475 


23.5I8' 


26.310 


.042520 


80 


13-593 


15.21 


.073565 


500 


24.146 


27.010 


.041414 


90 


13-845 


15-49 


.072230 


525 


24-775 


27.710 


.040364 


100 


14.096 


15-77 


.070942 


550 


25-403 


28.420 


•039365 


120 


14.592 


16.33 


.068500 


575 


26.031 


29.120 


.038415 


140 


15.100 


16.89 


.066221 


600 


26.659 


29.820 


.037510 


160 


15.603 


I7-50 


.064088 


650 


27.9I5 


31.230 


.035822 


180 


16.106 


18.02 


.062090 


700 


29.171 


32.635 


.034280 


200 


16.606 


18.58 


.060210 


750 


30.428 


34.040 


.032S65 


210 


16.860 


18.86 


.059313 


800 


31.681 


35-445 


.031561 


212 


16.910 


18.92 


.059135 


850 


32.941 


36.850 


.030358 


220 


17.111 


19.14 


.058442 


900 


34-197 


38.255 


.029242 


240 


17.612 


19.70 


.056774 


950 


35-454 


39.660 


.028206 


260 


18.116 


20.27 


.055200 


1,000 


36.811 


41.065 


.027241 


280 


18.621 


20 83 


.053710 


1,500 


49-375 


55-115 


.020295 


300 


19. 121 


21.39 


.052297 


2,000 


61.940 


69.165 


.016172 


320 


19.624 


21-95 


•050959 


2,500 


74-565 


83.215 


.013441 


340 


20.126 


22.51 


.049686 


3,000 


87.130 


97.265 


.OII499 



In column 3 the absolute pressure at constant volume is 



obtained from the equation 



p X t 



Pv, and for the pressure at 



360 from a constant volume from 62 ° F. we have ^"' — 

522.6 

o 



130 COMPRESSED AIR AND ITS APPLICATIONS. 

= 23.06, and so on for any desired temperature and pressure 

from the values of absolute pressure and temperature p and t. 

The 4th column of Table XV. is the weight of 1 cubic 

foot of free air at the temperatures in column 1. The expres- 

D y T 
sion — — — = D 1? in which D is the density of air or the weight 

of 1 cubic foot at 62 F., T the absolute temperature from 62 , 
and t the absolute temperature from any required temperature. 

Then for the density at 360 -°7 6o 97 X 566.6 _ <04 g 476> 

820.6 

For obtaining the volume of expansion for any temperature 
not found in the table, a proportional interpolation of quantities 
between the two nearest temperatures in the table will be found 
approximately near enough for all practical purposes. 

For the unit value of pressure, divide the greater value of 
expansion by the lesser, which gives the ratio due to the lesser 
pressure ; as, for example, the volume of one pound of air at 62 

9Q J 26 

is 13. 141, and the volume at 340 is 20. 126, and — - — = 1.531, 

13. 141 . 

which multiplied by the atmospheric pressure for the lesser 
volume, 14.7 X 1 - 5 3 1 = 22.51, the absolute pressure of a con- 
stant volume by an increase in temperature from 62 to 340 F. 
Its weight per cubic foot is also found by dividing the weight 
of the lesser volume in column 4, by the ratio as above, 1.531. 
For the cubic feet of one pound of air at any temperature, the 
weight of one cubic foot of air at 6o° F. multiplied by its abso- 
lute temperature, viz., .076097 X 522 = 39.7226, a constant by 
which the cubic feet of one pound of air at any other temper- 
ature may be readily computed. For example, in Table XV. 
the weight of one cubic foot at 62 F. = .0761 was used, which 
gives the constant 39.7242, Then the value of one pound in 

cubic feet at 32 is 492 — = 12.387, and for ioo° F. is 



39.7242 39-7 2 42 

— 14.097 cubic feet as found in the table. 

Another useful constant is derived from the sum of the 
weight of one cubic foot of air and its absolute temperature, 



THERMODYNAMICS. 131 

divided by the absolute atmospheric pressure 14.7. Thus say 

for 62 F. .0761 X 522°= 39.7242 as before, and J 9-/-4 — 

14.7 

2.70204, which may be used for the weight of one cubic foot of 
air at any pressure and temperature, by multiplying the con- 
stant by the absolute pressure and dividing the product by the 
absolute temperature. Thus, for the weight of one cubic foot 
of air at sixty pounds pressure and 62 ° F. temperature we have 

2.70204 X 74-7 = 866 d . 

522 



Chapter IX. 



ADIABATIC COMPRESSION 
AND EXPANSION 



ADIABATIC COMPRESSION AND EXPANSION. 

Having shown the relation of compression and expansion 
of air as a perfect gas under the isothermic law of Boyle as illus- 
trated in Fig. 42, the action of heat as evolved in compression 
and eliminated in expansion of air becomes a most important 
factor in the practical work of compression, transmission, and 
the utilization of air power. 

The adiabatic or isotropic lines or curves representing the 
moments of pressure due to the generation of heat by compres- 
sion or the elimination of heat by the expansion of air, may be 
computed and expressed in diagrammatic form from the formulas 
representing the varying conditions of increase or decrease of 
progressive pressure. The theoretical curves as derived from 
the equations represent the conditions when there is no absorp- 
tion of heat by the walls of a cylinder in which the operation is 
taking place. In practice this curve is never produced, but a 
modified form, lying between the theoretical and the isothermal, 
is the resultant as produced on an indicator card. 

The limiting point of heat by the compression of air is un- 
known, but is probably at the pressure of liquefaction, which 
has not yet been found with pressures up to 15,000 pounds per 
square inch and at temperatures raised in the experimental 
compressors and receivers. When air is once liquefied by press- 
ure and artificial cold, it has been found to hold its liquid state 
at about 12,000 pounds pressure per square inch at normal tem- 
perature, 6o° F. 

Cooling from the expansion of compressed air is inversely in 
the same ratio as from compression ; or, the temperature falls 
by the same scale that it rises. 

As we have said above, the heat saturation point is probably 
at the pressure of liquefaction ; so the cold extreme from expan- 



136 COMPRESSED AIR AND ITS APPLICATIONS. 

sion is probably at the absolute zero of expansion or perfect 
vacuum ; which is now accepted as the zero of absolute temper- 
ature, 460. 66° below the zero of the Fahrenheit scale. 

The difference of temperature by compression for equal in- 
crements of pressure is much greater in the lower part of the 
compression scale than in the upper part; as, for example, the 
increase of temperature from atmospheric pressure to one pound 
per square inch is io° F., while for an increase of one pound 
pressure from 99 to 100 pounds it is but 2.4 F. The differences 
of temperature when plotted on a pressure diagram form a para- 
bolic curve from its axis at absolute zero and terminating at 
infinite pressure and temperature ; the conditions within the 
limits of practice indicate this curve, as also its inverse order in 
the expansion of compressed air. 

Compression to the higher figures is not practicable by one 
stage compression, for at 1,000 pounds pressure the air rises to 
a full red heat, 13 13 F., and at 2,000 pounds to 1709 F. 

This is the theoretical temperature, but as much of the heat 
in the air would be absorbed by the compressor, it would soon 
become too hot for economical operation. 

The three elements involved in expressing the adiabatic con- 
dition of air or a gas are the pressure, volume, and absolute 
temperature. The quotient is always the same, however the 
pressure, volume, or temperature may change; given any two 
of these, the other may be readily determined ; for the absolute 
pressure at constant volume varies with the absolute temper- 
ature, (pv) oc T, and the volume at constant pressure also varies 
with the absolute temperature, (v) p oc T. Then in the work of 
air compression pv y is constant. 

Supposing that no attempt whatever is made to keep the air 
cool, and that the air is to be compressed in a cylinder which 
will neither take up any of the heat of itself, nor allow any to 
pass out of the air while it is being compressed ; this would be 
a case of adiabatic compression, and we should find that, when 
the volume had been reduced to one-half, the pressure would 



ADIABATIC COMPRESSION AND EXPANSION. 



137 



not be double only, as in the isothermal case, but more than 
double, because of the heat generated during compression being 
still in the air ; or, what comes to the same thing, when any 
given pressure is reached there would be a greater volume of 
air, owing to the heat in it, than had been found when compres- 
sion up to that same pressure had been isothermal. In making 
a diagram to show how the pressure varies in such a case, we 
must take into account not only the reduction of volume, but 
also the effect of the heat generated while that reduction is 
being made. The molecular theory helps us to understand 



< 1.1 u ->- 


■ 95 '1 ! \ , -7 










ill | ^^sC^^^**^ 


1 ! j 1 1 : Atmospheric Line 

Absolute Zero of Pressure. 



FIG. 44.— ADIABATIC COMPRESSION. 



why heat must be generated during both kinds of compression, 
for as soon as the piston begins to move it increases the energy 
of molecular vibration in the air contained by the cylinder, and 
is developed into activity and becomes sensible. 

A simple way of making a diagram of adiabatic compression 
is to draw the isothermal curve first (the dotted line in the fig- 
ure being the same as in Fig. 42), and then add to it, at various 
pressures, the extra volume due to the heat which has been 
generated while compressing up to that point. This extra vol- 
ume can be found by taking the natural number which corre- 
sponds to two-sevenths of the logarithm of the absolute pressure; 



138 COMPRESSED AIR AND ITS APPLICATIONS. 

which gives the ratio of volume after adiabatic compression, to 
volume due to isothermal compression. Thus at 2, 3, and 4 at- 
mospheres absolute the volumes would be 1.22, 1.37, and 1.48 
to 1 ; and as the power expended in delivery of air is propor- 
tional to the final volumes, this method of drawing the curve is 
useful. These numbers give also the final absolute temperature 
in terms of the absolute temperature before compression. In 
the equation to this adiabatic curve y — 1.406, being the ratio 
of the specific heats at constant volume and constant pressure. 
Then following the diagram, the 

Log. of 2 is 0.30103, which multiplied by f = 0.086 which is log. of 1.22 
" 3 "0.47712, " " f- 0.136 " 1.37 

" 4 " 0.60206, " " 1 = 0.172 " " " " 1.48 

and so on. 

Then to obtain the meeting of the adiabatic expansion curve 
with the atmospheric parallels, the differences of the logarithms 

for any two atmospheric pressures are multiplied by _ and 

their logarithmic indices will represent the volumes from the 
intersection of the isothermic curve with the atmospheric line ; 
so that to compute for the points in the curve of adiabatic 
expansion in Fig. 44 we have the 

log. of 7 atmospheres = 0.845098 

" 6 " =0.778151 

1.045 index 0.066947 

and — - — = .95, the proportion of adiabatic expansion to the 
1.045 

isothermal expansion on the line of 6 atmospheres. For the 
terminal of expansion in volumes of free air in proportion to the 
volumes of free air due to the adiabatic compression to 7 abso- 
lute atmospheres, then cooled to normal temperature, the log. 

of 7 = 0.845098 X — = 0.241456, index of which is 1.744, an( i 

7 

= -573 P er cen t of the isothermal volume of free air, as 



1.744 

shown in the diagram Fig. 44. In the more perfect formula for 



ADIABATIC COMPRESSION AND EXPANSION. 



139 



the heat curve of adiabatic compression of air, the terms for 
each increment of compression are equal to the product of the 
volume and pressure raised to the heat ratio of 1 .406, and the 
expression for each in- 

Volumes 

crement of pressure will ^ 
be pv 1406 , = Pl v, 1 - 406 , = ?0 

p. v. - or r" 6 = P.. - 

v i P 

where v is the greater 17 

volume and p x the great- 16 

er pressure. By using 15 

Naperian or c o m m o n u 

logarithms, the expres gls 

sion becomes 1.406 X I12 

v ,... pj 111 



log. 



log. 





\ 


\ 


\ 
















291.0 
279.$ 
204.5 
249.9 




\ 


\ 


\ 


















\ 


\ 




















\ 


\ 




\ 
















\ 






\ 




















\ 


\ 


\ 








1 






205.S 
19U 
176.1 
161.7 






\ 


\ 


\ 


















\ 


\ 


\ 










1 






\ 


\ 










































= \ 


=\ 








f 


132.3 
117.8 
102.9 
88.2 
73.3 
58.8 
11.1 








°°\ 


o\ 


6\ 






/ 










1 


\| 


\ * 


\ 


<s 














o\ 


\ 


\ 


§7 


e/ 

0/ 














A 


\ 


■£/ 


a 














\ 




i j 
















\ 




y 
















*y 




K x 












,* 






V 


\^ 




















N^S 


Os 


ft.0 



The thermal result 
of air compression and 
expansion is shown by 
the diagram Fig. 45. 
Both the temperature of 
the air and its volume 
are shown at different 
stages of compression. 
The simplest application 
of this diagram is that 
which gives the gauge 
pressure represented at 

different points of the stroke. This- is shown in the horizontal 
lines. But in compressing air we produce heat, and it is impor- 
tant to know the temperature at any given pressure, also the 
relative volume. All of these are shown in the diagram. The 
initial volume of air equal to one is taken and divided into ten 
equal parts, each division between two vertical lines, shown by the 
figures at the top, representing one-tenth of the original volume. 






s s i i s 

Temperature Fahrenheit 
FIG. 45.— ADIABATIC DIAGRAM. 



§ § 



140 COMPRESSED AIR AND ITS APPLICATIONS. 

The vertical and horizontal lines are the measures of vol- 
umes, pressures, and temperatures. The figures at the left in- 
dicate pressure in atmospheres above a vacuum ; the corre- 
sponding figures at the right denote pressures by the gauge. At 
the top are volumes from one-tenth to one ; at the bottom de- 
grees of temperature from zero to i,ooo° F. The two curves 
which begin at the lower left-hand corner and extend to the 
upper right are the lines of compression. 

These curves start from atmospheric pressure, and in all 
computations for pressure the zero of atmospheric pressures is 
the starting-point, which would be represented by an additional 
line at equal distance of the other lines, below the bottom line. 

The upper curve is the "adiabatic" curve, or that which 
represents the pressure at any point on the stroke, with the 
heat developed by compression remaining in the air ; the lower 
is the "isothermal," or the pressure curve uninfluenced by heat. 
The three curves which begin at the lower right-hand corner 
and rise to the left are heat curves, and represent the increase 
of temperature corresponding with different pressures and vol- 
umes, assuming in one case that the temperature of the air be- 
fore admission to the compressor is zero, in another 6o°, and in 
another ioo°. 

Beginning with the adiabatic curve, we find that for one 
volume of air, when compressed without cooling, the curve in- 
tersects the first horizontal line at a point between 0.6 and 0.7 
volume, the gauge pressure being 14.7 pounds. If we assume 
that this air was admitted to the compressor at a temperature of 
zero, it will reach about ioo° when the gauge pressure is 14.7 
pounds. If the air had been admitted to the compressor at 6o°, 
it would register about 176 at 14.7 pounds gauge pressure. 
If the air were ioo° before compression, it would go up to about 
230 at this pressure. Following this adiabatic curve until it 
intersects line No. 5, representing a pressure of five atmospheres 
above a vacuum (58.8 pounds gauge pressure), we see that the 
total increase of temperature on the zero heat curve is about 



ADIABATIC COMPRESSION AND EXPANSION. 141 

270 ; for the 6o° curve it is about 370 ; and for the ioo° curve 
it is about 435 . The diagram shows that when a volume of air 
is compressed adiabatically to 2 1 atmospheres (294 pounds gauge 
pressure), it will occupy a volume a little more than one-tenth ; 
the total increase of temperature with an initial temperature of 
zero, is about 650 ; with 6o° initial temperature it is 8oo°, and 
with ioo° initial it is 900 . It will be observed that the zero 
heat curve is flatter than the others, indicating that when free 
air is admitted to a compressor cold, the relative increase of tem- 
perature is less than when the air is hot. This points to the 
importance of low initial temperature. It is plain that a high 
initial temperature means a higher temperature throughout the 
stroke of a compressor. The diagram gives the loss of temper- 
ature during compression from initial temperatures of o°, 6o°, 
ioo°. If we compare the compression line from zero with the 
compression line from ioo°, we observe that in compressing the 
air from, say, 1 atmosphere to 10 atmospheres, the original dif- 
ference, which at the start was only ioo°, has now been about 
doubled, that is, it has reached 200 ; and in carrying the com- 
pression to 20 atmospheres, the difference now becomes about 
250 . Each horizontal division represented by the figures at 
the bottom is equal to ioo°, and the space between any two 
adjacent horizontal lines may be subdivided into 100 equal parts 
representing i° each. 

Where there is a system of cooling the air during compres- 
sion, the lines on the indicator cards can be traced between the 
adiabatic and isothermal curves on the diagram. In practice, 
the best compressors show a line about midway between these 
two curves. 

For all practical purposes in using this diagram, it is best to 
follow the adiabatic curve in all determinations, except where 
the exact pressure line is known. This diagram will be found 
convenient to those who are called upon to figure the pressure 
at different points in the stroke of an air compressor, and it 
points out the common error of neglecting to take into consid- 



142 COMPRESSED AIR AND ITS APPLICATIONS. 

eration in one's figures the fact that, at the beginning of the 
stroke, one atmosphere in volume already exists. Beginning 
at the lower left-hand corner, the adiabatic pressure curve in- 
tersects the first horizontal line at that point in the stroke where 
the pressure on the gauge will register 14.7 pounds. 

The next horizontal line shows where the gauge reaches 
29.4 pounds, and it is evident here that the piston of an air 
compressor travels much farther in reaching 14.7 pounds than 
in doubling that pressure or in reaching 29.4 pounds; thus an 
air compressor is an engine of unevenly distributed resistance. 
During the early stages of the stroke it has a slowly accumulating 
load to carry, while later on this load is multiplied very rapidly. 

For computing the pressure at the intersection of the adia- 
batic curve with the horizontal lines in the diagram, the lines 
representing the volumes of compression are the starting-points 

in the formula, and the compression —__,_, etc., of which 

10 10 

the complements -5., — , etc., are the terms of the volume used 
10 10 

in the equation. Then by inversion, — = 2. and — = i.iii 

v, P 9 

log. 0.045714 X 1.406 = log. 0.064273, of which the index is 
1. 159 in absolute atmospheres, and 1.159— 1 = .159 in hun- 
dredths of the space above one atmosphere at the intersection 

of the first vertical line representing a compression of — and 

marked .9 at the top of the diagram. For the position of the 
curve at the second vertical line and following the same nota- 
tion is to be used, viz., — = 1.25 log. 0.0961 X 1.406 = log. 
8 

0.136255, of which the index is 1.368 in absolute atmospheres 
and 1.368 — 1 = .368 in hundredths of the space at the inter- 
section of the second vertical line representing a compression of 

— and marked .8 at the top of the diagram. At the compres- 
sion of — and marked . 1 in the extension of the diagram the 
10 



ADIABATIC COMPRESSION AND EXPANSION. 1 43 

point of intersection with the adiabatic curve will be carried up 
to 25.47 atmospheres. 

For locating the isothermic curve the first index of the com- 
pressions is to be used, and the intersections of the curve 

with the verticals will be — = i.iii absolute atmospheres and 
9 

i.iii — i = . in on the scale of the diagram , — = 1.25 — 1 = 

.25, and so on for each intersection on the isothermic curve 
with the compression verticals of the diagram. 

For the temperature curves from three different initial tem- 
peratures of o°, 6o°, and ioo°, the temperature of compression 
for each increment or atmosphere as represented in the diagram 
is found by the common logarithm of the quotient of the abso- 
lute pressures multiplied by the exponent of the ratio of ex- 

0.29 rp 

pansion by heat, .2906. Then -i- = — X 100 to correspond 

with the ioo° divisions at the bottom of the diagram; and for 
the gauge pressure of 14.7 pounds, which is 2 absolute atmos- 
pheres as marked on the left-hand margin, -2lz is 2, log. 

0.30103 X .29 = log. 0.0033298, the index of which is 1.08 X 

100 = 108, the point of meeting of the expansion curve with 

the horizontal line representing 2 atmospheres absolute. 

Then for the curve starting at 6o°, or 520 absolute, we 

, lU .j 1.08 X 520 w c 01^-0 

have the same index — = 1.22 X 100 = 122 -|- 60 , 

460 

the starting-point in the scale, = 182 the point of intersec- 
tion of the 6o° heat curve with the horizontal line of 2 at- 
mospheres absolute. Again for the curve starting at an initial 

temperature of ioo° F. we have the same index J. — 

F • 460 

= 1.3 1 5 X ioo° = 1 3 1. 5 + 100 as the starting-point = 231.5, 

the point of meeting of the curve from ioo° initial temperature 

with the horizontal line of 2 atmospheres absolute. And so on 

throughout the diagram. 



144 COMPRESSED AIR AND ITS APPLICATIONS. 

There is a slight difference in the results from the equations 
of various authors for the mean pressure from air compression. 
The following formula is different from the one used in Mr. 

Shone 'stables— Tables XVI., XVII.: _JL_ P f'fi) *LZ± _ i~| 

n — i Lvp/ n J 

n 1.406 r 1 n— 1 rn1 

= mean pressure. = ^ ■ = 3.463 and = .29. Then 

n— 1 .406 n 

for compressing air from atmospheric pressure to 60 pounds 

gauge pressure P = 14.7 and P 2 = 74.7. Then 3.463 X 14.7 X 

( ) — i- I = mean pressure, which must be worked out 

as follows: The ratio of the pressures illZ = 5.08 log. 

14.7 

0.705864 X .29 = 0.2047005 index 1.602 — 1 = .602 X 14.7 X 

3.463 = 30.63, the mean pressure of adiabatic compression 

from atmospheric pressure to 60 pounds gauge pressure. 



COMPRESSED AIR TABLES. 

In Table XVI. is given the absolute pressure in pounds per 
square inch from the zero of pressure to 3,014.7 pounds absolute 
in column 1 on the left, and the gauge pressure inversely from 
a vacuum to o or atmospheric pressure, and up to 3,000 pounds 
in column 8 at the right side of the table. 

Column 2 is the absolute temperature, Fahrenheit, of com- 
pression from the absolute zero of temperature up to normal 
temperature at atmospheric pressure, and so on to 3,014.7, 

and is by the formula (2) X (461.2 -J- T) in Fahrenheit 

degrees. 

Column 3 == (column 2 — 461.2) = t — 461. 2. ° Fahrenheit 
t = column 2. 

Column 4 is the absolute temperature in Centigrade de- 
grees = t = (2 \ X (274+T) in Centigrade degrees. 

Column 5 = t — 274 or column 4 — 274 C. Centigrade t = 
column 5. 



ADIABATIC COMPRESSION AND EXPANSION. 



145 



Column 6 is the adiabatic compression of 100 volumes = 



column 7 X 



or column 7 X 



col. 2 



461.2 +T 521, 

Column 7 is the isothermal compression of 100 volumes = 
P X 100 _ 14.7 X ioo^ 

p column 1 

The tables were originally computed by Mr. Shone in Eng- 
land up to 100 pounds gauge pressure, using the absolute tem- 
peratures of 461.2 and 2 74 C. The error is too small to warrant 
a recomputation, and for symmetry the author has used the 
same formula for the extension to 3,000 pounds. 



TABLE XVI. — Pressures, Temperatures, and Volumes by Adiabatic and 
Isothermal Air Compression. (Shone.) 



•3* 


of .J 

m 0) £ 
£> G..C 


ag a % 


Absolute 
temperature, 
Centigrade. 


lit 

gi « 


Volumes from 

zoo at 

atmospheric 

pressure, 

adiabatic. 


Volumes from 

100 at 

atmospheric 

pressure, 
isothermal. 


6 


I 


2 


3 


4 


5 


6 


7 


8 


O.O 


O.O 


— 461.20 


0.00 


— 274.00 


Infinite. 


Infinite. 


- 14-7 


I. 


+ 239- 5 


— 222.15 


+ 132.81 


- 141. 19 


674.21 


1,470.00 


- 13- 


7 


2. 


292.27 


- 168.93 


162.36 


— in. 64 


412.16 


735- 


— 12 


7 


3- 


328.74 


- 132.47 


182.63 


- 91-37 


309.06 


490. 


— 11 


7 


4- 


357-34 


— 103.86 


198.52 


- 75.48 


251.96 


367.50 


— 10 


7 


5- 


381-23 


- 79.98 


211.79 


— 62.21 


215.04 


294. 


— 9 


7 


6. 


401.93 


- 59-27 


223.29 


- 50.71 


188.93 


245- 


- 8 


7 


7- 


420.30 


- 40.90 


233-50 


- 40.50 


169-35 


210. 


- 7 


7 


8. 


436.90 


- 24.65 


242.72 


— 31.28 


154-03 


183-75 


- 6 


7 


9- 


452.08 


- 9.12 


251.16 


— 22.84 


141.67 


163.333 


- 5 


7 


10. 


466. 10 


+ 4.90 


258.94 


— 15.06 


131.46 


147. 


— 4 


7 


11. 


479-17 


18.06 


266.21 


- 7-79 


122.86 


133.636 


- 3 


7 


12. 


491.41 


30.21 


273.02 


— 0.98 


"5.50 


122.50 


— 2 


7 


13- 


502.95 


41-75 


279-41 


+ 5-41 


109.12 


113.077 


— 1 


7 


14. 


513.88 


52.69 


285.49 


11.49 


103.53 


105. 


— 


7 


14.7 


521.20 


60.00 


289.56 


15-56 


roo.oo 


100. 







15-7 


531-24 


70.04 


295-13 


21.13 


95-435 


93.63I 


1 




16.7 


540.84 


79.64 


300.47 


26.47 


9 r -34i 


88.024 


2 




17.7 


550.04 


88.84 


305.58 


31.58 


87.646 


83.051 


3 




18.7 


558.88 


97.68 


310.49 


36.49 


84.292 


78.610 


4 




19.7 


567.38 


106.18 


315-21 


41.21 


81.231 


74.619 


5 




20.7 


575-59 


"4-39 


319-77 


45-77 


78.443 


71.031 


6 




21.7 


583.52 


122.32 


324-18 


50.18 


75.842 


67.742 


7 




22.7 


591-19 


129.99 


328.44 


54-44 


73-454 


64.758 


8 




23-7 


598.63 


137-43 


332.57 


58.57 


71.240 


62.025 


9 




24.7 


605.85 


144.65 


336.58 


62.58 


69.180 


59-5^4 


10 




25-7 


612.86 


151.66 


340.48 


66.48 


67.258 


57.I98 


11 




26.7 


619.68 


158.48 


344.27 


70.27 


65-459 


55.056 


12 




27.7 


626.33 


165-13 


347.96 


73.96 


63-773 


53-069 


13 




28.7 


632.80 


171.60 


35L56 


77.56 


62.187 


51.220 


14 





146 



COMPRESSED AIR AND ITS APPLICATIONS. 
TABLE XVI. {Continued). 



a ■ 


ii 3 3 




2 s-o 


9 

5 w 


2 |«-a 


-Jgi 




S> 3 




U 0.3 


2. cS u 


U H Sh 


mOj^ 5tj 


3-lts! 


bfl3 


« 

,Q 1> 


lis 


s oJ'£ 


O j- be 


£"0 


<U &« 

3 2 <S.S5 


^s 


3 m 
P. 


I 


2 


3 


4 


5 


6 


7 


8 


29.7 


639.12 


177.92 


355-07 


81.07 


60.693 


49-495 


15- 


30 


7 


645.29 


184.09 


358.49 


84.49 


59-283 


47-883 


16 




31 


7 


65I-3I 


190,11 


361.84 


87.84 


57-949 


46.372 


17 




32 


7 


657.21 


196.01 


365.12 


91.12 


56.685 


44-954 


18 




33 


7 


662.97 


201.77 


368.32 


94-32 


55-485 


43.620 


19 




34 


7 


668.62 


207.42 


371-46 


97.46 


54-345 


42.363 


20 




35 


7 


674-15 


212.95 


374-53 


100.53 


53.260 


41.176 


21 




36 


7 


679-57 


218.37 


377-54 


103.54 


52.225 


40.054 


22 




37 


7 


684.89 


223.69 


380.49 


106.49 


51-238 


38.992 


23 




33 


7 


69O.II 


228.91 


383-39 


109.39 


50.295 


37-984 


24 




39 


7 


695-23 


234.03 


386.24 


112.24 


49-392 


37.028 


25 




40 


7 


700.27 


239.07 


389.04 


115-04 


48.527 


36.118 


26 




4i 


7 


705.22 


244.02 


391-79 


117.79 


47.698 


35-252 


27 




42 


7 


710.08 


248.88 


394-49 


120.49 


46.902 


34.426 


28 




43 


7 


714-36 


253.66 


397-15 


123.15 


46.136 


33-638 


29 




44 


7 


719-57 


258.37 


399-76 


125.76 


45.402 


32.886 


30 




45 


7 


724.20 


263.00 


402.33 


128.33 


44.695 


32.166 


3i 




46 


7 


728.76 


267.56 


404.87 


130.87 


44-OI3 


3L478 


32 




47 


7 


733-25 


272.05 


407-36 


I33-36 


43-356 


30.818 


33 




48 


7 


737-68 


276.48 


409.82 


135.82 


42.722 


30.185 


34 




49 


7 


742.04 


280.84 


412.24 


138.24 


42.110 


29- 577 


35 




50 


7 


746.34 


285.14 


414-63 


140.63 


41.518 


28.994 


36 




5i 


7 


750-58 


289.38 


416.99 


142.99 


40.947 


28.433 


37 




52 


7 


754-76 


293.56 


419.32 


145-32 


40.393 


27.894 


38 




53 


7 


758.88 


297.68 


421.60 


147-60 


39.858 


27.374 


39 




54 


7 


762.95 


301.75 


423.86 


149.86 


39-339 


26.874 


40 




55 


7 


766.97 


305.77 


426.09 


152.09 


38.836 


26.391 


4i 




56 


7 


770.94 


309.74 


428.30 


154-30 


38.349 


25.926 


42 




57 


7 


774-86 


313.66 


430.48 


156.48 


37.876 


25-477 


43 




53 


7 


778.73 


317-53 


432.63 


158.63 


37.4I6 


25.043 


44 




59 


7 


782.56 


321.36 


434.76 


160.76 


36.970 


24.623 


45 




60 


7 


736.33 


325-13 


436.85 


162.85 


36.537 


24.217 


46 




61 


7 


790.07 


328.87 


438.93 


164.93 


36.115 


23.825 


47 




62 


7 


793.76 


332.56 


440.98 


166.98 


35.706 


23-445 


48 




63 


7 


797-41 


336.21 


443.01 


169.01 


35-307 


23.077 


49 




64 


7 


801.02 


339-82 


445.01 


171. 01 


34-918 


22.720 


5o 




65 


7 


804.59 


343-39 


446.99 


172.99 


34- 540 


22.374 


5i 




66 


7 


808.13 


346.93 


448.96 


174-96 


34-172 


22.039 


52 




67 


7 


811.62 


350.42 


450.90 


176.90 


33-813 


21.713 


53 




68 


7 


815.08 


353-88 


452.82 


178.82 


33-462 


21.397 


54 




69 


7 


818.50 


357-30 


454.72 


180.72 


33-I2I 


21.090 


55 




70 


7 


821.89 


360.69 


456.61 


182.61 


32.787 


20. 792 


56 




7r 


7 


825.25 


364.05 


458.47 


184.47 


32.462 


20. 502 


57 




72 


7 


828.57 


367.37 


460.32 


186.32 


32.144 


20.220 


58 




73 


7 


831.86 


370.66 


462.14 


188.14 


3I.834 


19.946 


59 




74 


7 


835.11 


373-91 


463-95 


189.95 


31-531 


19,679 


60 




75 


7 


838.34 


377-14 


465-74 


191.74 


31-235 


19.419 


61 




76 


7 


84I-54 


380.34 


467.52 


193-52 


30.945 


19.166 


62 




77 


7 


844. 70 


383.50 


469.28 


195-28 


30.662 


18.919 


63 




78 


7 


847-84 


386.64 


471.02 


197.02 


30.385 


18.679 


64 




79 


7 


850.95 


389.75 


472.75 


198.75 


30.113 


18.444 


65 




80 


7 


854.04 


392.84 


474-47 


200.47 


29.848 


18.216 


66 




81 


7 


857.09 


395-89 


476.16 


202.16 


29.588 


17-993 


67 





ADIABATIC COMPRESSION AND EXPANSION. 
TABLE XVI. {Continued). 



H7 



a) 6 
$ 

■° £ 

<! a 


.a ft_£ 


£°o£n 

ftges 


£,X 

ski 1 

20 


9 

s g g 
£^0 


Volumes from 
100 at 

atmospheric 
pressure, 
adiabatic. 


Volume, from 

100 at 

atmospheric 

pressure, 
isothermal. 


M3 

a! w 

z 

ft 


1 


2 


3 


4 


5 


6 


7 


8 


82.7 


860.I2 


398.92 


477-84 


203.84 


29-334 


17-775 


68. 


83 


7 


863.12 


401.92 


479-51 


205.51 


29.084 


17-563 


69 




84 


7 


866.IO 


404.90 


481.17 


207.17 


28.840 


17-355 


70 




85 


7 


869.05 


.407-85 


482.81 


208. Si 


28.601 


I7.I53 


7i 




86 


7 


871.98 


410.78 


484-43 


210.43 


28.366 


16.955 


72 




87 


7 


874-89 


413-69 


486.05 


212.05 


28.136 


16.762 


73 




88 


7 


877.77 


4i6.57 


487.65 


213-65 


27.911 


16.573 


74 




89 


7 


880.63 


419-43 


489.24 


215.24 


27.689 


16.388 


75 




90 


7 


883.46 


422.26 


490.81 


216.81 


27-472 


16.207 


76 




9i 


7 


886.28 


425.08 


492.38 


218.38 


27.259 


16.031 


77 




92 


7 


889.07 


427.87 


493-93 


219.93 


27.050 


15.858 


78 




93 


7 


891.84 


430.64 


495-47 


221.47 


26.845 


15.688 


79 




94 


7 


894-59 


433-39 


496.99 


222.99 


26.643 


15-523 


80 




95 


7 


897.32 


436.12 


498.51 


224.51 


26.445 


15.361 


81 




96 


7 


9OO.03 


438.83 


500.02 


226.02 


26.251 


15.202 


82 




97 


7 


902.72 


441-52 


501.51 


227.51 


26.060 


15.046 


83 




98 


7 


905-39 


444.19 


502.99 


228.99 


25.872 


14.894 


84 




99 


7 


908.04 


446.84 


504-47 


230.47 


25.687 


14. 744 


85 




100 


7 


9IO.67 


449.47 


505-93 


231-93 


25.506 


14.598 


86 




IOI 


7 


913.28 


452.08 


507.38 


233-38 


25.328 


14-454 


87 




102 


7 


915.88 


454-68 


508.82 


234.82 


25.I52 


I4.3I4 


88 




103 


7 


918.46 


457.26 


510.26 


236.26 


24.980 


14.176 


89 




104 


7 


921.02 


459.82 


511.68 


237.68 


24-753 


14.040 


90 




105 


7 


923-56 


462.36 


513-09 


239.09 


24.643 


13.907 


9i 




106 


7 


926.08 


464.88 


514-49 


240.49 


24.479 


13-777 


92 




107 


7 


928.59 


467.39 


515.88 


241.88 


24.318 


13.649 


93 




108 


7 


931.08 


469.88 


5I7-27 


243-27 


24-159 


13-523 


94 




109 


7 


933.56 


472.36 


518.64 


244.64 


24.002 


13.400 


95 




no 


7 ■ 


936.02 


474.82 


520.01 


246.01 


23.848 


13.279 


96 




III 


7 


938.46 


477-26 


521.37 


247.37 


23.696 


13.160 


97 




112 


7 


940.89 


479.69 


522.72 


248.72 


23-547 


13.044 


98 




"3 


7 


943-31 


482.11 


524.06 


250.06 


23-399 


12.929 


99 




114 


7 


945-71 


484.51 


525.39 


251-39 


23.254 


12.816 


100 




119 


7 


957-44 


496.24 


53L9I 


257-91 


22.558 


12.280 


105 




124 


7 


968.91 


507.71 


538.27 


264.27 


21.893 


11.788 


no 




129 


7 


980.11 


518.91 


544- 5o 


270.50 


21.304 


H-333 


115 




134 


7 


990. 80 


529.60 


55o.8o 


276.80 


20.822 


10.913 


120 




139 


7 


1,001.22 


540.02 


556.23 


282.23 


20.202 


10.522 


125 




144 


7 


1,011.64 


550.44 


562.02 


288.02 


19.718 


10.159 


130 




149 


7 


1,021.55 


560.35 


567.53 


293-53 


19.245 


9.819 


i35 




154 


7 


1,031.19 


569.99 


572.88 


298.88 


18.794 


9.502 


140 




159 


7 


1,041.86 


580.66 


578.81 


304.81 


18.391 


9.205 


145 




164 


7 


1,049.95 


588.75 


583.30 


309.30 


17.974 


8.925 


150 




174 


7 


1,068.35 


607.15 


593-53 


3I9-53 


17.240 


8.414 


160 




184 


7 


1,085.66 


624.46 


603. 14 


329.14 


16.576 


7.958 


170 




194 


7 


1,102.59 


641.39 


612.55 


338.55 


15.968 


7-550 


180 




204 


7 


1,118.49 


657.29 


621.38 


347-38 


I5.403 


7.181 


190 




214 


7 


1-134-23 


673.03 


630.12 


356.12 


14.896 


6.846 


200 




264 


7 


1,205.48 


744.28 


669.71 


395-71 


12.838 


5-553 


250 




314 


7 


1,267.08 


805.88 


703.93 


429.93 


"•355 


4.671 


300 




364 


7 


1,332.96 


871.76 


740.53 


466. 53 


10. 304 


4.030 


35o 




414 


7 


1,372.89 


911.69 


762.71 


488.71 


9-334 


3-544 


400 




464 


• 7 


i,4i7-7o 


956.5o 


787.61 


513-61 


8.603 


3-163 


45o 





148 



COMPRESSED AIR AND ITS APPLICATIONS. 



TABLE XVI. (Continued). 









s*fS 

P.g g 0) 


of . 

So 




*°*>£ 

°* ^2 

P.SS 

5 a 

£- 


Volumes, from 

100 at 

atmospheric 

pressure, 

adiabatic. 


Volume from 

100 at 
atmospheric 

pressure, 
isothermal. 


ft 


1 


2 


3 


4 


5 


6 


7 


8 


514-7 


1,461.49 


1,000.29 


811.94 


537-94 


8.008 


2.856 


500. 


614.7 


1,538.84 


1,077.64 


854-91 


580.91 


7.058 


2.391 


600. 


714-7 


1,607.64 


1,146.44 


893-13 


619.13 


6.340 


2.056 


700. 


814.7 


1,669.92 


1,208.72 


927.73 


653.73 


5.780 


1.S04 


800. 


914.7 


1,726.78 


1,265.58 


959-32 


685.32 


5-324 


1.607 


900. 


1,014.7 


1,774-42 


1,313.22 


985-79 


711.79 


4.928 


1.448 


1,000. 


1,214.7 


1-875.32 


1,414.12 


1,041.84 


767.84 


4-353 


1. 210 


1 . 200. 


I.4I4-7 


1,959-71 


1,498.51 


1,088.73 


Si+73 


3.880 


1.032 


1,400. 


1,614.7 


2,024.71 


1,563-51 


1,124.84 


850.84 


3-534 


0.910 


1,600. 


1,814-7 


2, 106.63 


i,645.43 


1,170.35 


896.35 


3-274 


0.810 


1,800. 


2,014.7 


2, 171.05 


1,709-85 


1,206.14 


932.14 


3.036 


0.729 


2,000. 


2,514-7 


2,3i5-i7 


1,853-97 


1,286.20 


1,012.20 


2-594 


0.584 


2, 500. 


3,014.7 


2,440.41 


1,979.21 


i,355.78 


1,081.78 


2.280 


0.4S7 


3,000. 



In Table XVII. are given the gauge pressure ; ratios of com- 
pression in volumes adiabatic and isothermal ; points of stroke 
at gauge pressure, adiabatic; points of stroke at gauge pressure, 
isothermal; the mean pressure at full stroke adiabatic and iso- 
thermal, for compression from 1 pound to 3,000 pounds. 

Column 1 = gauge pressure, p — P. 

Column 2 — 100 -=- by the mean pressure at full stroke, adi- 
abatic, as found in column 6, Table XVI., and represents the 
ratio of volumes at atmospheric pressure from gauge pressure, 
adiabatic. 

Column 3 = 100 -r- by column 7 in Table XVI., and repre- 
sents the ratio of volumes at atmospheric pressure from gauge 
pressure, isothermal. 

Column 4 = 1 -r- by column 2 in this table, and represents 
the point of stroke of a piston at the moment the gauge pressure 
is reached, adiabatic. 

Column 5 = 1 -=- by column 3 in this table, and represents 
the point of stroke of a piston at the moment the gauge press- 
ure is reached, isothermal. 
i+H 



Column 6 = pX 



R 



P, in which R is the ratio of the 



ADIABATIC COMPRESSION AND EXPANSION. 



149 



adiabatic compression in column 2 of this table and H = the 
hyperbolic logarithm of the ratio R in column 2 of this table, 
i. + H 



Column 7 = p X 



R 



P ; in which R is the ratio of iso- 



thermal compression found in column 3, and equals ±- or absolute 

pressure divided by the normal pressure. H = the hyperbolic 

logarithm of the ratio of isothermal compression £ in column 3 

of this table. 

In the absence of tables of hyperbolic logarithms, the com- 
mon logarithm of a number X 2.302585 = hyperbolic logarithm. 



TABLE XVII.— Gauge Pressures, Ratios of Compression, Points of Stroke, 
and Mean Pressure for Full Stroke in Air Compression. (Shone.) 








*" t3 h <U °S ° 


' af 0" ° 


©OS 


sl-a 


sl-1 


ft 


p4 g •? -d 


J* jj £ g ^ a 

cd ^ O a, ^h CL +. 


bos cS c-i 


v *-■ S 

3 0) S) 

kg 


_ *■■ J: 35 


$ £ " « 

^1 




oS 


oi — c 


c 




«s 


tj~ 


I 


2 


3 


4 


5 


6 


7 


I 


I.0478 


1.06S0 


954 


936 


0.978 


0.967 


2 


I 


0948 


1.1361 


•913 


880 


1-937 


1.874 


3 


I 


1409 


1. 2041 


.876 


831 


2.846 


2.680 


4 


I 


1864 


1. 2721 


843 


786 


3.805 


3-513 


5 


I 


2310 


1. 3401 


812 


746 


4.615 


4-303 


6 


I 


2748 


1.4078 


784 


710 


5-419 


5-055 


7 


I 


3185 


1.4762 


75S 


677 


6.326 


5.762 


8 


I 


3614 


1.5442 


735 


648 


7.101 


6-347 


9 


I 


4037 


1. 6122 


712 


620 


7-865 


7.000 


10 


I 


4455 


1.6803 


692 


595 


8-737 


7.626 


11 


I 


4868 


1-7483 


673 


572 


9-479 


8.226 


12 


I 


5277 


1. 8164 


655 


55i 


10. 21 1 


8.802 


13 


I.5681 


1.8844 


638 


53i 


10.934 


9.280 


14 


1. 608 1 


1-9524 


622 


512 


11.647 


9.817 


15 


I.6476 


2.0204 


607 


495 


12.353 


10.336 


16 


1.6S68 


2.0884 


593 


479 


13.049 


10.837 


17 


1-7257 


2.1565 


579 


464 


I3-738 


11.320 


18 


1. 7641 


2.2245 


567 


450 


I4-3I4 


n.723 


19 


1.8023 


2.2925 


555 


436 


14.990 


12.180 


20 


1. 8401 


2.3605 


543 


424 


I5-657 


12.623 


21 


1.8776 


2.4286 


533 


412 


16.317 


13.052 


22 


1.9148 


2.4966 


522 


401 


16.870 


13-470 


23 


I-95I7 


2.5646 


512 


390 


17.516 


13.818 


24 


1.9883 


2.6327 


503 


380 


18.157 


14.215 


25 


2.0246 


2.7007 


494 


370 


18.695 


14.602 


26 


2.0607 


2.7687 


485 


361 


19.324 


14.976 


27 


2.0965 


2.8367 


477 


353 


19.946 


15-344 


28 


2.1321 


2.9048 


469 


344 


20.470 


15-651 


29 


2.1675 


2.9728 


461 


336 


21.081 


16.002 


30 


2. 


2025 


3.0408 


454 


329 


21-597 


16.345 



150 



COMPRESSED AIR AND ITS APPLICATIONS. 
TABLE XVII. {Continued). 



6 

3 $ 


.io of 
me at 
spheric 
ssure, 
l batic. 


tio of 
me at 
spheric 
ssure, 
ermal. 

Dint 


? ill 


Dint 

roke at 
luge 
ssure, 
ermal. 


ean 
ssure 
stroke, 
batic. 


m to <u 


*l 


oj S a>.3 




\^l\ 
3 


.S3 


p.-H'S 


tx£ 
ts"" 


I 


2 


3 


4 


5 


6 


7 


31 


2.2374 


3.1088 


•447 


.322 


22. 199 


16.679 


32 


2.2721 


3.1769 


.440 


•3i5 


22.704 


17.006 


33 


2.3065 


3.2449 


•434 


.308 


23.295 


17.281 


34 


2.3407 


3-3129 


■427 


.302 


23-794 


17-594 


35 


2-3747 


3-3810 


.421 


.296 


24.288 


17.903 


36 


2.4086 


3-449° 


•415 


.290 


24.865 


18.204 


37 


2.4422 


3.5I70 


.409 


.284 


25-352 


18.500 


38 


2-4757 


3.5S50 


.404 


.279 


25-923 


18.790 


39 


2.5089 


3-6531 


•399 


• 274 


26.402 


19.032 


40 


2.5420 


3-72H 


393 


.269 


26.878 


I9-3II 


4i 


2-5749 


3-7S9I 


388 


.264 


27.350 


19.586 


42 


2.6076 


3.8571 


383 


• 259 


27.905 


19-855 


43 


2.6402 


3-9252 


379 


• 255 


28.370 


20.118 


44 


2.6726 


3.9932 


374 


.250 


28.834 


20.342 


45 


2.7049 


4.0612 


370 


.246 


29.295 


20.598 


46 


2.7370 


4.1293 


365 


.242 


29-833 


20.849 


47 


2.7689 


■ 4.1973 


361 


• 238 


30.285 


21.096 


48 


2.8007 


4-2653 


357 


• 234 


30.737 


21-339 


49 


2.8323 


4-3333 


353 


.231 


31.187 


21-544 


5o 


2.8638 


4.4014 


349 


.227 


31.632 


21.780 


5i 


2.8952 


4.4694 


345 


.224 


32.154 


22.012 


52 


2.9264 


4-5374 


342 


.220 


32.594 


22.040 


53 


2-9575 


4.6054 


338 


.217 


33-033 


22.465 


54 


2.9884 


4-6735 


335 


.214 


33-468 


22.656 


55 


3-oi93 


4.7415 


331 


.211 


33-90I 


22.873 


56 


3.0499 


4.8095 


328 


.208 


34-33Q 


23.089 


57 


3.0805 


4.8776 


325 


.205 


34-758 


23.301 


58 


3.1110 


4.9456 


321 


.202 


35-I83 


23.511 


59 


3-I4I3 


5.0136 


318 


.199 


35.607 


23.688 


60 


3-I7I5 


5.0816 


315 


.197 


36.027 


23.892 


61 


3.2016 


5-1497 


312 


.194 


36.448 


24.092 


62 


3-23I5 


5-2177 


309 


.192 


36.864 


24.292 


63 


3.2614 


5-2857 


307 


.189 


37.277 


24.487 


64 


3-2911 


5-3537 


304 


.187 


37.690 


24.653 


65 


3.3208 


5.4218 


301 


.184 


38.098 


24.844 


66 


3-3503 


5.4898 


298 


.182 


38.509 


25-033 


67 


3-3797 


5.5578 


296 


.180 


38.914 


25.219 


68 


3-409I 


5-6259 


293 


.178 


39-317 


25.403 


69 


3-4383 


5-6939 


291 


.176 


39.720 


25-559 


70 


3-4674 


5-76I9 


288 


.174 


40.121 


25.738 


7i 


3.4964 


5.8299 


286 


.172 


40.518 


25.916 


72 


3-5253 


5.8980 


284 


.170 


40.913 


26.093 


73 


3-5541 


5.9660 


281 


.168 


41-237 


26.264 


74 


3-5829 


6.0340 


279 


.166 


41-631 


26.411 


75 


3-6II5 


6.1020 


277 


.164 


42.021 


26.582 


76 


3.6400 


6. 1 701 


275 


.162 


42.411 


26.750 


77 


3.6685 


6.2381 


273 


.160 


42.797 


26.916 


78 


3.6969 


6.3061 


271 


.159 


43-182 


27.079 


79 


3-725I 


6.3742 


268 


• 157 


43.566 


27.218 


80 


3-7533 


6.4422 


266 


• 155 


43.882 


27.379 


81 


3-7814 


6.5102 


264 


• 154 


44. 260 


27.538 


82 


3.8094 


6.5782 


263 


• 152 


44.639 


27.695 


83 


3.8373 


6. 6463 


261 


.150 


45-OI7 


27.851 


84 


3-8652 


6.7143 


259 


.149 


45-393 


27.983 



ADIABATIC COMPRESSION AND EXPANSION. 



151 



TABLE XVII. {Continued). 








u 









<a . 




Ratio of 

volume at 

atmospheri 

pressure, 

adiabatic. 


Ratio of 

volume at 

atmospheri 

pressure, 

isothermal 

Point 


" 
> <D l-TJ 

CS ti <S 

;-s3 


Point 
of stroke a 

gauge 

pressure, 

isothermal 


Mean 

pressure 

at full strok 

adiabatic. 


D m w a> 


1 


2 


3 


4 


5 


6 


7 


85 


3.8929 


6.7823 


• 257 


.147 


45-700 


28.136 


86 


3.9260 


6.8503 


• 255 


.146 


46.137 


28.286 


87 


3.9482 


6.9184 


• 253 


.145 


46.443 


28.436 


88 


3-9757 


6.9864 


252 


• 143 


46.813 


28.584 


89 


4.0032 


7-0544 


250 


.142 


47-115 


28.709 


90 


4.0306 


7.1224 


248 


.140 


47.482 


28.855 


9i 


4-0579 


7-1905 


246 


• 139 


47-487 


28.999 


92 


4.0851 


7-2585 


245 


.138 


48.209 


29.141 


93 


4. 1 1 22 


7-3265 


243 


.136 


48.507 


29.282 


94 


4-1393 


7-3946 


242 


• 135 


48.869 


29.401 


95 


4. 1663 


7.4626 


240 


• 134 


49.227 


29-541 


96 


4.1932 


7.5306 


238 


• 133 


49.522 


29.678 


97 


4.2201 


7.5986 


237 


.132 


49.878 


29.813 


98 


4.2469 


7.6667 


235 


.130 


50.234 


29.948 


99 


4.2736 


7-7347 


234 


.129 


50.525 


30.063 


100 


4.3003 


7.8027 


233 


.128 


50.878 


30.195 


105 


4-433 


8-143 


225 


.123 


• 52.451 


30.824 


no 


4-567 


8.483 


219 


.118 


54-034 


31-427 


115 


4-693 


8.823 


213 


• "3 


55-662 


32.004 


120 


4.802 


9.163 


208 


.109 


57-351 


32.552 


125 


4-950 


9-503 


202 


.105 


58.656 


33-091 


130 


5-071 


9-843 


i97 


.102 


60.153 


33-615 


135 


5-195 


10.184 


192 


.098 


61.587 


34.102 


140 


5-328 


10.524 


188 


.095 


62.650 


34-649 


145 


5-437 


10.864 


184 


.092 


64.199 


35.062 


150 


5-563 


11.204 


179 


.089 


65.706 


35.368 


160 


5.800 


11.884 


172 


.084 


68.369 


36.312 


170 


6.033 


12.565 


166 


.080 


70.926 


37.293 


180 


6.263 


13-245 


i59 


.076 


73-491 


37.966 


190 


6.492 


13-925 


i54 


.072 


76.797 


38.706 


200 


6.713 


14-605 


149 


.068 


78.189 


39-463 


250 


7.789 


18.007 


128 


•055 


89.035 


42.475 


300 


8.806 


21.408 


113 


•047 


98.780 


44.998 


35o 


9.705 


24.808 


103 


.040 


108.276 


47.189 


400 


10.713 


28.210 


093 


.035 


115.889 


49.039 


45o 


11.623 


31.612 


086 


.032 


123.594 


50.776 


500 


12.487 


35.014 


080 


.029 


131-423 


52.262 


600 


14.168 


41.816 


070 


.024 


143.646 


54-822 


700 


15-773 


48.618 


063 


.021 


155-541 


57.055 


800 


17.301 


55-422 


058 


.018 


166.163 


58.948 


900 


18.783 


62.224 


053 


.016 


176.929 


60.671 


1,000 


20.292 


69.027 


049 


.014 


185.703 


62.214 


1,200 


22.972 


82.632 


043 


.012 


203.824 


64.862 


1,400 


25-773 


96.238 


039 


.010 


219.442 


67.069 


1,600 


28.296 


109.843 


035 


.009 


232.994 


68.941 


1,800 


30. 543 


123.449 


033 


.008 


247.705 


70.772 


2,000 


32.938 


137-054 


030 


.007 


260.105 


72.133 


2,500 


38.550 


171.068 


026 


.006 


289.327 


75-326 


3,000 


43-859 


205.081 


023 


.005 


313.902 


78.152 



Chapter X. 



THE COMPRESSED AIR 
INDICATOR CARD 



THE COMPRESSED AIR INDICATOR CARD. 

The theoretical conditions of air compression and expan- 
sion may be diagrammatically expressed to represent both the 
theoretical and the practical lines of compression and expansion, 
with the difference that the theoretical lines or curves may be 
computed from the known law of thermodynamics, but the 
practical lines or curves must be found and based on the heat- 
absorbing element of the compressor, which is an uncertain 




Fig. 46.— compressed air indicator card. 



amount depending much on the velocity of the pistons, or rather 
the velocity of transmission through the compressor and the de- 
gree of absorption of heat by the walls of the cylinder. 

Referring to Fig. 46 we have the adiabatic or heat line A-B, 
which represents the work done if there were no cooling effect 
in the cylinder, the line A-C representing the actual work done 
in the cylinder, and the isothermal or constant temperature line 
A-B, which is the line the indicator would make if all the heat 
generated could be carried off during the work of compression. 

This latter condition does not exist in our high-speed ma- 
chines of to-day, but one can imagine it to exist in a machine 
where the piston travels slow enough to allow all the heat to be 
carried off by the water jacket or by radiation. In following the 
movement of the piston in the cylinder, suppose it starts at A, 



156 COMPRESSED AIR AND ITS APPLICATIONS. 

the cylinder then being full of free air, and moves to the right; 
the pressure in the cylinder at any point is represented on line 
A-C. When the piston reaches C, it has compressed the air to 
the receiver pressure, and it must then push the compressed air 
out through the discharge valves into the receiver. Owing to 
the weight of the discharge valves and the tension of the springs 
holding them to their seats, the pressure in the cylinder reaches 
a few pounds above the receiver pressure before the valves open, 
as shown at E, and there gradually drops to the receiver press- 
ure at the end of stroke, the irregularities in the line being due 
to the fluttering of the discharge valves and the vibration of the 
indicator arm. 

The piston, having reached the end of stroke, comes to a 
standstill while the crank is passing the dead centre ; and as the 
current of air that held the discharge valves open in passing out 
of the cylinder has ceased, the discharge valves close by the 
tension of the springs back of them. The piston now starts to 
recede — the air under pressure that was left in the cylinder 
due to the clearance space expanding until it becomes atmos- 
pheric pressure at F, when the inlet valves open and the cylin- 
der is filled with free air. If the indicator line follows along 
the atmospheric line, we know that the inlet area is not re- 
stricted and we are getting a volume of free air at atmospheric 
pressure represented by the travel of piston from F to A, this 
representing the actual free air capacity of the compressor. 
The volume between G and F representing the air contained 
in the clearance space, expanded, is lost as far as the capacity of 
the compressor is considered ; and although this air required 
work in compressing it to 75 pounds pressure, it has given out 
its work in expanding, helping to compress the air on the other 
side of the piston. 

The only loss in work due to the clearance space is that re- 
sulting from the small amount of cooling that the confined air 
has been subjected to, its volume, when hot, having been a trifle 
more and having required more work to compress it; but this is 



THE COMPRESSED AIR INDICATOR CARD. I 57 

rarely taken into account. We thus see that the clearance 
space in the cylinder is not a loss of power, but a loss of capac- 
ity, which is allowed for by deducting anywhere from 3 to 6 per 
cent of the cylinder volume, according to the design of the air 
cylinder and the length of stroke of same — it being evident 
that the longer the stroke for the same size cylinder the less 
will be the percentage of clearance. On some indicator cards it is 
noticed that the intake air pressure falls below the atmospheric 
line, showing that the air inlet is restricted, or, as is common 
on air cylinders having poppet inlet valves closed by a spring, 
the tension of the spring when the piston is moving slow at the 
end of the stroke will close the valves before the piston has 
completed its stroke., so that when the end of stroke is reached 
a partial vacuum is formed in the cylinder. Where these de- 
fects exist, the piston must travel a distance of A-0 before the 
atmospheric line is reached, and the volume of the cylinder 
would be O-F, instead of A-F, making the 6-per-cent allowance 
for clearance necessary, while 2 to 3 per cent should be suffi- 
cient on a well-designed compressor. 

The temperature of the air at 75 pounds gauge pressure 
without any cooling is 419 , although this is somewhat lower in 
the cylinder, due to the jacket cooling; and from actual readings 
on thermometers placed in the discharge pipe close to the cylin- 
der, the temperature is from 300 to 360 , according to the size 
and speed of the compressor. 

Referring again to Fig. 46 we have the volume C-K-N-G, 
representing about 25 per cent of the free air volume at, say, 
320 temperature, to put into the receiver at each stroke of the 
compressor piston. As the receiver is anywhere from 10 to 20 
feet from the compressor, and as it has a large surface exposed 
for radiation, its temperature will be considerably less than 
that of the air leaving the cylinder, which will consequently be 
cooled and reduced in volume ; and as the air is generally used 
a considerable distance from the compressor, it will have 
reached atmospheric temperature by the time it is used, and the 



158 COMPRESSED AIR AND ITS APPLICATIONS. 

original volume C-K-N-G, when leaving the cylinder, will have 
shrunk to D-K-L-G by the time it is used, being then only 
if of what it would have been, had the air been used hot di- 
rectly as it left the compressor. So that the actual loss by 
shrinkage within the cylinder of a compressor of the best con- 
struction may be no more than from 2 to 3 per cent of the vol- 
ume together with the clearance of an average from all causes, 
say of 3 per cent, which with the cooling by transmission brings 
the volume of free air entering the compressor to about 16 per 
cent at 75 pounds gauge pressure. 

THE MEAN PRESSURE OF AN INDICATOR CARD. 

The indicator is the proper instrument for investigating the 
internal work of compressing air, and the indicator card is the 
best representation of the work of the compressor. 

In Fig. 47 is shown a facsimile of an indicator card from a 
22 by 30 inch air cylinder running at 50 revolutions per minute 
and delivering air into a receiver at 80 pounds per square inch 
pressure. It will be seen that the sum of all the pressures in 
the divisions of the card amount to 541, which divided by the 
number of division measurements, 15, = 36 pounds per square 
inch as the mean pressure of the whole stroke. The usual 
practice is to divide the card into ten parts, but we have used 
fifteen, which gives a more satisfactory result; and even twenty 
parts gives a truer mean pressure. By comparing the mean 
pressure from the indicator card with the mean theoretical 
pressure in column 6 of Table XVII., which for 80 pounds gauge 
pressure is 43.88 pounds, it will be seen that a difference of 7.88 
pounds exists, which is due to the absorption of heat by the 
walls of the air cylinder, clearance, and a possible leakage. It 
will also be seen that the isothermal mean pressure in column 
7, Table XVII., for 80 pounds gauge pressure is theoretically 
27.37 pounds, and the difference from the mean pressure of the 
indicator card is '8.63 pounds, so that with these figures the loca- 



THE COMPRESSED AIR INDICATOR CARD. 



59 



tion of the terminals of the adiabatic and isothermal curves can 
be established, and from which the actual efficiency of the com- 
pressor can be found for the speed at which it was running 
when the card was taken. For this card the speed was 50 revo- 
lutions per minute, which was but two-thirds the speed due to its 
full work. It may be noted here that the mean pressure due to 
287 



the curve only, is 



11. 8 



24.3 pounds, and that the mean press- 



ure for isothermal compression due to the curve only for 80 
pounds terminal is 27.37 — .155 X 80 = 14.97 pounds. The 




HE INDICATOR CARD. 



difference 24.30 — 14.97 = 9.33 represents the difference of the 
terminals of the actual and the isothermal curves in pressure 
terms. The mean pressure due to a perfect adiabatic compres- 
sion, by Table XVII., column 6, for 80 pounds gauge pressure 
would be 43.88 pounds, and for isothermal compression 27.37 as 
per column 7, same table ; their difference 16.51—9.33 = 7.18, 
the mean of which is 35.62, a little less than shown on the 
measured card. This indicates the fact that the compressor by 
its slow speed absorbed less than one-half the heat generated 
by compression as indicated by the numbers 9.33 and 7.18; on 
the other hand the indicator card shown at Fig. 46 appears to 



l6o COMPRESSED AIR AND ITS APPLICATIONS. 

have been taken from a quick or normal speed of the compres- 
sor, and shows the actual compression curve considerably above 
the mean, only about one-third of the heat of compression being 
absorbed during the stroke of compression. 

The falling-ofl of the line of delivery at the top of the cards 
indicates in part the absorption of heat from the air and the 
relief of the valve opening to the receiver pressure, which is 
always found to be from one to three pounds less than the com- 
pression pressure on the card. 

THE STEAM AND AIR CARD. 

In Fig. 48 is illustrated a combined steam and air indicator 
card, showing the reason for and answer to the oft-repeated ques- 
tion as to how it is possible to compress air to 80 or 100 pounds 




Fig. 48.— steam and air card. 

pressure with 60 pounds or less steam pressure with equal-sized 
cylinders. The reason is plainly shown in the comparative 
areas of the steam and air card, and from the computed mean 
engine pressure of each from actual measurement for pressures 
which show enough excess of power in the steam card to over- 
come the friction of the compressor and give it the required 
motion. The M. E. P. of the air card divided by the M. E. P. 
of the steam card shows 90 per cent efficiency, or that 10 per cent 
of the power of the steam used has been absorbed in the mov- 
ing parts pertaining to both cylinders. In many of the best 
designed compressors, the difference shown in the steam and 
air cards has ranged from 5 to 6 per cent. What is made up in 



THE COMPRESSED AIR INDICATOR CARD. l6l 

the air card by high pressure is represented in the steam card 
by greater volume. It will be noticed that the central points of 
pressure in each card do not coincide, and that the minimum 
pressure in the steam cylinder occurs at the moment of maxi- 
mum pressure in the air cylinder. This condition would check 
the operation of an air compressor but for the retaining power of 
the fly-wheel, the momentum of which carries the air piston to 
the end of its stroke, thus equalizing the motion of all the mov- 
ing parts of a compressor. This condition is due to the high- 
pressure impulse of the steam piston being transmitted to the 
fly-wheels, in which it is stored and given out during the high- 
pressure work of the air piston. 

The fly-wheel does more than this : its weight gives uni- 
formity of motion to the compressor, so much to be desired in a 
continuously moving machine. 



Chapter XI. 



ACTUAL WORK OF THE 
COMPRESSOR 



ACTUAL WORK OF THE COMPRESSOR. 

No compressor of the piston type of modern construction can 
produce the conditions required by the theoretically adiabatic 
or isothermal lines in columns 6 and 7 in Table XVII. The 
mean pressure practically is always between these two lines, and 
in most compressors runs nearer to the adiabatic than to the 
isothermal line ; and also varies in the same compressor with 
the speed and the efficiency of the water-jacket. In a high- 
speed compressor the mean pressure nears the adiabatic line, 
while with a slow speed and rapid cold-water circulation in the 
jacket it is possible to obtain a mean less than half the dif- 
ference of the adiabatic and isothermal curves, time being 
a considerable element in fixing the curve of compression. 
It is only with compressors of the old Dubois and Francois 
type with water injection and water-filled clearance, and the 
hydraulic compressor of Sommeiller, that the isothermal line 
was nearly or quite reached ; and later with the hydraulic pit 
compressors of the Frizell and Taylor type has it been possible 
to reach the fall line of isothermal compression, and even under 
differences in temperature of the air and water, to produce a 
condition of compression of air and its delivery below the at- 
mospheric temperature. 

In Table XVIII. we have endeavored to show the practical 
operation of air compression with a single compression from 5 
to 120 pounds by intervals of 5 pounds gauge pressure, with an 
assumed absorption of four-tenths of the heat of compression. 
In column 2 of the table the mean pressure for full stroke is 
obtained from six-tenths of the difference between the isother- 
mal and adiabatic mean pressures found in columns 6 and 7, 
Table XVII. , added to the isothermal mean pressure in column^. 



1 66 



COMPRESSED AIR AND ITS APPLICATIONS. 



TABLE XVIII. — Of the Mean Pressure and the Relative Load of Com- 
pression and Delivery in Terms of the Mean Pressure of the Whole 
Load, for the Actual Operation of a Compressor at Medium Speed 
with Ample Water Circulation in the Jacket of Cylinder and Heads, 
due to the estimated absorption of t % of the heat of compression 

FROM 6o° F. 



Gauge 
pressure, 
pounds. 


Mean 
pressure for 
full stroke. 


Pressure due 

to delivery 
in part of the 
whole stroke. 


Mean p 

COmP cu e rv 1 e° n ° £ of strc 
in part of the V re J 
whole stroke. 


oint 

)ke when 
sure is 
iched. 


Temperature 

of 

discharge 

from 6o° F. 


I 


2 


3 


4 


5 


6 


5 


4-49 


3-92 


o.57 


785 


87° 


IO 


8.29 


6-53 


1.76 


665 


112 


15 


H-54 


8-43 


3-H 


562 


130 


20 


14.44 


9.90 


4-54 


495 


148 


25 


17-05 


11. 10 


5-95 


444 


164 


30 


19.49 


12.12 


7-37 


404 


178 


35 


21-73 


12.98 


8-75 


371 


192 


40 


23-85 


13-72 


10.13 


343 


204 


45 


25.81 


14.40 


11. 41 


320 


216 


5o 


27.69 


15.00 


12.69 


300 


227 


55 


29.48 


15.56 


13-93 


2S3 


238 


60 


31-17 


16.38 


14-79 


273 


247 


65 


32-79 


16.64 


16.15 


256 


257 


70 


34-36 


17.42 


16:94 


242 


266 


75 


35.84 


18.52 


17.32 


231 


275 


80 


37.28 


19.60 


17.68 


221 


283 


85 


38.67 


20.57 


18.10 


213 


292 


90 


40.03 


21.67 


18.36 


204 


300 


95 


41-35 


22.64 


18.71 


197 


307 


IOO 


42.60 


23.70 


18.90 


189 


314 


I05 


43.80 


24.48 


19.32 


184 


321 


IIO 


44-99 


25-33 


. 19.66 


178 


329 


115 


46.20 


26.30 


19.90 


173 


335 


120 


47-43 


27.27 


20.16 


168 


342 



Column 3 is obtained from six-tenths of the difference of the 
points of stroke in columns 4 and 5, Table XVII., for adiabatic 
and isothermal compression, added to the point of stroke for 
isothermal compression, column 5, and the sum multiplied 
by the pressure in column 1, which is equal to the part of the 
whole mean pressure due to delivery. Column 4 is equal to 
the part of the whole mean pressure due to the curve of com- 
pression only, and is found by column 2 — column 3 == column 
4. Column 5 is the assumed point of stroke, found by adding 
six-tenths of the difference of the adiabatic and isothermal points 
of stroke in columns 4 and 5 in Table XVII., and the isother- 
mal point of stroke in column 5 of the same table. Column 



ACTUAL WORK OF THE COMPRESSOR. 



I6 7 



6 represents the temperature of the air from the compressor 
delivery valves, when four-tenths of the heat of compression 
from 6o° F. has been absorbed by the cooling appliances and 
walls of the cylinder, and is obtained from column 3, Table 
XVI., — 6o° F. x to °f tn ^ s i ncrease of temperature and 6o° 
added to the product. 



THE WORK OF AIR COMPRESSION. 

It is often desired to find the amount of mechanical work 
which air receives during compression only, and also the work 
of the whole stroke of a piston for isothermal and adiabatic com- 
pression ; we therefore illustrate in Fig. 49 an isothermal in- 
dicator card with the area 
of compression only, 
shaded to give to the eye 
a comprehensive compari- 
son with the work of de- 
livery shown by the rec- 
tangle following the point 
of compression stroke. 

The curve of compres- 
sion as represented in the 

diagram is that of a hyperbola, one of the properties of which is 
that the areas of the rectangles contained by the horizontal and 
vertical ordinates from the several points in the curve as at P, 
P\ P 2 , P 3 , are always the same, that is, all the pressures and 
volumes products (p, v), absolute rectangles, are equal in area; 
as further explained in the article on isothermal compression. 
Then for the work of compression from atmospheric or normal 
pressure (14.7) to any desired pressure, the increments of com- 
pression to the end of the stroke become a numerator in the frac- 
tion of the whole stroke, and their quotient becomes the ratio of 
which the hyperbolic logarithm multiplied by the pressure of 
the normal atmosphere upon a square foot equals the foot- 




SOMF.TRICAL CARD. 



l68 COMPRESSED AIR AND ITS APPLICATIONS. 

pounds required for compression. Thus, for compressing one 
cubic foot of air from atmospheric pressure to two atmospheres, 

we have -I- = Ji- = 2, the hyperbolic logarithm of which is 
P 14.7 

.6931 X 2,116.8 — 1,467.15 foot-pounds per cubic foot of air 

compressed isothermally from atmospheric pressure to 14.7 

pounds per square inch. 

For any number of pounds pressure the ratio is obtained in 

the same way, viz., say for 75 pounds gauge pressure, 1- = ~^-L 

P 14.7 

= 6.1 as given in column 3, Table XVII. The hyperbolic 

logarithm of 6.1 =1.8083X2,116.8 = 3,827.8 foot-pounds. 

Then J ' w/ = . 116 of a horse power, theoretical, to compress 
33,000 

one cubic foot of air per minute to 75 pounds gauge pressure; 
to which must be added the friction of the compressor. 

The foot-pound work isothermally per pound of air is ob- 
tained by multiplying the foot-pounds for one cubic foot by the 
number of cubic feet in a pound at atmospheric temperature ; 
thus at 62 in Table XV'., 13.141 cubic feet = 1 pound, and 
13. 141 X 3,827.8 = 50,301 foot-pounds. 

Analyzing the isometrical card, Fig, 49, for the work due to 
compression only, and the work due to delivery as shown on the 
diagram; we find the whole work at 4 atmospheres absolute or 

44. 1 pounds gauge pressure to be as follows ; then — = 4 hyp. 

log. = 1.3863 X 2,116.8 = 2,934.5 foot-pounds per cubic foot, 
and 44.1 X 144 = 6,350.4 X .25 stroke = 1,587.6 foot-pounds 
in delivering 1 cubic foot of free air when compressed iso- 
thermally to 44. 1 pounds per square inch gauge pressure. Then 
2,934.5 — 1,587.6= 1,346.9 foot-pounds expended in compres- 
sion only, for 1 cubic foot of free air at 44.1 pounds gauge 
pressure. 

Adiabatic compression reaches a much higher theoretical 
work value, while the actual work of compression has an inter- 



ACTUAL WORK OF THE COMPRESSOR. 



mediate work value depending upon the amount of heat absorp- 
tion by the walls of the compressor. 

In Fig-. 50 is shown the theoretical card of adiabatic com- 
pression for 4 atmospheres absolute, 44. 1 pounds gauge press- 
ure, and in the shaded part the comparative work due to the 
curve of compression only, while the work of delivery is repre- 
sented in the unhatched rectangle. 

The formula for the work of compression for the complete 
stroke of a compressor is derived from the difference in temper- 
ature multiplied by the mechan- 
ical equivalent of air at constant 
pressure, Mcp = 184.7. Then 
T, — T X 184.7 = W, the work. 
The difference in temperature 
may be obtained by the differ- 
ence of absolute temperatures 
in column 2, Table XVI., and 
the mechanical equivalent for 
air is derived from the Joule equivalent multiplied by the 
specific heat of air; 778 X .2375 = 184.7. 

In the case of the diagram Fig. 50, the work of compression 
of one pound of air from 6o° F. temperature to 4 atmospheres 
absolute or 44. 1 pounds per square inch gauge pressure will be 
T 2 — T, or t — T as in column 2, Table XVI., or by the formula 
used for that column as before stated. The absolute temper- 
ature, 779 — 52 1 = 258 X 184.7 = 47,652.6 foot-pounds per 
pound of free air. Then for the work per cubic foot of free air 
at 6o° F. divide the number of foot-pounds per pound by the 
number of cubic feet of free air in Table XV. at 6o° per pound 




ADIABATIC CARD. 



of air. Then 



47,652.6 



3,637 foot pounds and 



13. 1 33.000 

of a horse power per cubic foot, to which must be added the 
proportional friction of the compressor. The work of compres- 
sion due to delivery and to the compression curve separately is 
of interest. The point of stroke of the piston at which the 



I 70 COMPRESSED AIR AND ITS APPLICATIONS. 

pressure is reached may be taken from column 4, Table XVII., 
for gauge pressure, or may be computed by the ratio of the ab- 



solute pressures from the formula, log. 



P v, -. 1 

t- = — and . 

P v log. inde 



x 

.0 o 

= the point of stroke. As, for example, ^— = 4, the ratio for 

14.7 

the absolute pressures. 

The common log. for 4 is 0.60206 X .711=0.42806, the 

log. index of which is 2.68, and — — = .373, the point of 

2.68 

stroke from the terminal when full pressure is reached. 

The whole number of foot-pounds when divided by the vol- 
ume of one pound of air in cubic feet, for the temperature of 
the free air taken into the compressor, equals the foot-pounds 

per cubic foot. Then 4 ' ' ■ > "' — 3,637.6 foot-pounds per cubic 

[ 3- 1 
foot of free air at 6o° F. compressed to 4 atmospheres or 44. 1 
gauge pressure ; and as the mean pressure for 44. 1 is 28.9 pounds 
per square inch, and the point of stroke for the full stroke is 
.373 from the terminal, then 44.1 X .373 = 16.45, which is the 
proportion of the mean pressure due to delivery. 

2 S Q 

Then — '-?- = 1.756, the ratio of the foot-pounds due to de- 
16.45 

livery, to the total foot-pounds per pounds of air. Then •*' 3 

1.756 

= 2,071 foot-pounds for the delivery, and 3,637 — 2,071 = 1,566 

foot-pounds due to the adiabatic compression curve of the card. 

This method can be applied to the actual work of the com- 
pressor by using the relative pressures in columns 2,3, and 4 
in Table XVIII., which are based on actual conditions of a com- 
pressor in which four-tenths of the heat of compression is ab- 
sorbed during compression. 

Table XIX. has been computed by the formula and examples 
on page 167 of the work of isothermal compression for column 2 
for pressures of every 5 pounds as in column 1. Column 3 has 
been computed by the formula and examples on page 169 of the 



ACTUAL WORK OF THE COMPRESSOR. 



171 



work of adiabatic compression, and column 4 represents the 
actual foot-pound work of compression per cubic foot of free air 
in compressors that absorb four-tenths of the heat due to com- 
pression, and has been obtained from six-tenths of the differ- 
ence of columns 2 and 3 added to the isothermal foot-pound 
work in column 2. 

TABLE XIX. — Foot-Pounds of Work Required for Compressing Air. 
Theoretical for Columns 2 and 3, and for the Actual Conditions 
with Partial Cooling in Column 4 as Found in Table XVIII. For 
One-Stage Compression. 





Foot- 


Foot- 


Foot- 




Foot- 


Foot- 


Foot- 


Pressure 


pounds 


pounds 


pounds 


Pressure 


pounds 


pounds 


pounds 


in 


per cubic 


per cubic 


per cubic 


in 


per cubic 


per cubic 


per cubic 


pounds. 


foot. 


foot, 


foot, 


pounds. 


foot, 


foot, 


foot, 




isothermal. 


adiabatic. 


actual. 




isothermal. 


adiabatic. 


actual. 


I 


2 


3 


4 


I 


2 


3 


4 


5 


619.6 


649-5 


637-5 


55 


3,393-7 


4,188.9 


3,870.8 


10 


1,098.2 


1, 192.0 


i,i54-6 


6o 


3,44o.4 


4,422.8 


4,029.8 


15 


1,488.3 


i,66i.2 


1, 592.0 


65 


3.577-6 


4,645-4 


4.218.2 


20 


I. 817.7 


2,074.0 


i,97i-4 


70 


3,706.3 


4,859-6 


4,398.i 


25 


2, 102.6 


2,451.6 


2,312.0 


75 


3,828.0 


5,063.9 


4,569-5 


30 


2,353-6 


2,794-o 


2,617.8 


80 


3,942.9 


5,259-7 


4.732.9 


35 


2,573.o 


3,111.0 


2,897.8 


85 


4,051-5 


5,45o.o 


4,89 \ 6 


40 


2,780.8 


3.405-5 


3,155-6 


93 


4,155-7 


5,633-i 


5,042.1 


45 


2,966.0 


3,681.7 


3,395-4 


95 


4,254-3 


5,8 9-3 


5,187.3 


5o 


3,136.2 


3,942.3 


3,619.8 


100 


4,348.1 


5,981.2 


5,327-9 



Other equations or formulas may be used for obtaining the 
foot-pounds of work required to compress air to any desired 
pressure. For example, the adiabatic volume 

V the adiabatic vol. . .. „ V 406 _ t 

T" 



the adiabatic vol. , V 

. . . and — 

initial vol. v 



Then the ratio of the absolute volumes raised to the power of 
.406 logarithmically is equal to the ratio of the temperatures 

V 



GO 



also — = ( P) and 
v Vp/ 

are also logarithmic ratios from which the press- 



due to the equivalent compression 
t 



ure is derived from the volumes and the temperature from 
the relative pressures. 



V 



Then for working the equation — = — we may use the 
Table XVII.; in column 2 we find the adiabatic ratio of 14.7 



1/2 COMPRESSED AIR AND ITS APPLICATIONS. 

gauge pressure by interpolation to be 1.64, the log. of which is 
0.21484 X .406 = 0.087225, the index of which is 1.222, which 
is equal to the ratio of the absolute temperatures as found in 

column 2, Table XVI., or ^L. = 1.2222 . 

522 

Again we have (P J = — as explained before. 
For the work of compression we have 

w= 1^406 d r T (P- 29 -iV 
.406 Vp / 

In which — — = 3.438, a constant, d R = the difference 

.406 

of the foot-pound equivalents of specific heat at constant press- 
ure, Mcp= 184.77, an d the specific heat at constant volume 
Mcv= 13 1.6, which = 53.17, and T = the normal absolute 
temperature from 6o° F. = 522 . 

For example, to obtain the foot-pound work for adiabatic com- 
pression from 6o° F. to two absolute atmospheres, or 14.7 pounds 
gauge pressure, we have as per equation above 3.438 X 53. 17 X 

522 X ( 9'4 — 1 \ — the foot-pounds for one pound of free air, 
\14.7 / 

and this product divided by 13. 1 = the foot-pounds of work per 

cubic foot. The operation will then be for the last term of the 

equation "^-4 = 2, the logarithm of which is 0.30103 X .29 = log. 

0.08729, the index of which is 1.2225, an d 1.2225 — l = .2225. 
The total product will then be 21,231 foot-pounds per pound of 

air, and — '"° = 1,620 foot-pounds per cubic foot of free air 

! 3- l 
compressed from 6o° F. to 14.7 pounds gauge pressure. This 
differs slightly in amount from the method of computation by 
temperatures on account of not carrying out fully the decimal 
system. 

The saving in foot-pound work by compressing air that is 
moist even to saturation has been demonstrated, by experiments 



ACTUAL WORK OF THE COMPRESSOR. I 73 

made in France by M. Mallard, to be 5^ per cent at 3 atmos- 
pheres, 7^ per cent at 4 atmospheres, 11 per cent at 5 atmos- 
pheres, and 12 per cent at 7 atmospheres. This should be 
observed as an advantage in foot-pound work by compressing 
air in rainy or foggy weather. 



Chapter XII. 



MULTI-STAGE 
AIR COMPRESSION 



MULTI-STAGE AIR COMPRESSION. 

The great range of pressures through which compressed air 
is used, calls for pressures varying from i pound, to 3,000 or more 
pounds per square inch ; but the greatest field of its work is 
found between 50 and 100 pounds gauge pressure. Even at 
100 pounds the greatest economy of production is found in the 
two-stage effect, which eliminates to a large degree the heat- 
resisting power acquired during the second half of the piston 
stroke in a single-stage compressor. For higher pressures the 
economy of two-stage compression is largely increased up to 
500 pounds, and with three-stage compression up to 1,000 
pounds, and with four-stage compression up to 3,000 pounds. 

The great heat generated by single compression to high 
pressures is apparent by referring to Table XVI., where it will 
be seen that the single-compression temperature for a pressure 
of 200 pounds reached 673 F., which is above the melting- 
point of lead, and will fire woodwork. The effect of such 
great heat on the packing and lubricants of a compressor are 
apparent; hence the necessity for a two-stage process with in- 
tercooling when compressing air to above 100 pounds pressure. 
The heat of single-stage compression is graphically shown in 
the diagram Fig. 45, where the temperatures are shown for dif- 
ferent free air intakes at o°, 6o°, and ioo° F., and the heat of 
compression temperatures at the pressures of atmospheres up to 
21 and of pounds gauge pressure up to 294. Of course the ab- 
sorption of heat by the cylinder walls modifies the temperature 
somewhat, but the fire pump before described shows that press- 
ures from air at the ordinary temperature of a room will ignite 
combustibles at above 350 pounds pressure. 

The introduction of water into the cylinder as formerly prac- 



1/8 COMPRESSED AIR AND ITS APPLICATIONS. 

tised has had but little practical effect, and unless introduced in 
quantities to keep down the temperature does not add to heat 
economy, and in large quantities adds to the cost of work. The 
manner and time of injection greatly affect its usefulness in cool- 
ing the air, so that if drawn in by the suction of the piston its 
spraying effect is lost by its contact with the cool incoming air, 
and the spray can only wet the walls and piston at best. If it 
is forced in as a fine spray at the moment that the compression 
has raised the temperature enough to be absorbed by the water, 
say through the last half of the stroke, it requires power and the 
operation of a pump, at a cost that seriously affects the economy 
of the water-injection system. Besides the entanglements ap- 
pertaining to this method of obtaining compressed air at moder- 
ately high pressures, the compressed air is loaded with moisture 
which is not all dropped in the receiver, in active operations, 
but is carried along the transmission pipes in a misty or satu- 
rated condition, and becomes a nuisance in the exhaust of oper- 
ating machines. The uncertainty of the quantity of water 
entering a cylinder with a quick-working piston is a source of 
danger from concussion, and finally the wear and tear of w r ater- 
injection cylinders from the inability to obtain pure water has 
been one of the principal causes of the abandonment of this 
class of compressors by experienced builders. 

TWO-STAGE COMPRESSION. 

The practice of two-stage compression for moderate press- 
ures, say to ioo pounds, has been long in use in the compressors 
of the Norwalk Iron Works, with a fair claim for economy over 
the increased friction from the second cylinder. For pressures 
above ioo pounds further compounding becomes necessary, as a 
matter of both economy and safety. Safety being in some cases 
an important element in eliminating as far as possible the lia- 
bility of explosive effect from high temperature and its effect 
upon the oil of lubrication, this will be discussed further on. 

In Fig. 5 i is shown an outline card of two-stage compres- 



MULTI-STAGE AIR COMPRESSION. 



179 



sion to 75 pounds in which the maximum pressure of over 80 
pounds was reached in order freely to deliver the air through 
exit valves of restricted area. The depressed inlet curve of the 
second-stage card shows one of the losses in multiple compres- 
sion, which is due to the small area of the intercooler, its con- 
nections, valves, and to the shrinkage of volume by the inter- 
cooler, which, if its capacity is not equal to isothermal cooling, 
causes a loss in the work of the second cylinder. With cooling 
receivers of large capacity the continuous working value of the 
second cylinder rises to its proper function, and the inlet card 

















! 


Ih 


-™ 


^% 
















: J 




















1 








| 












f 


/ < 


s/- 


____ 


.___ 


?4 
















































1 












At 


Ons/il 


eric 1 


ine 


























j 












Abso 


ute Z 


ro.Pi 


i'Mic 







Fig. 51.— two-stage card. 

lines come more near to the delivery line of the first-stage 
cylinder. The possibilities of economy may then rise from 4 
per cent to about 1 5 per cent of the work lost by heat in two- 
stage compression, above the isothermal work. 

The heat loss by one-stage compression to 80 pounds from 

6o° F. is equal to 5^_59^v3»94- _i -34 per centofthe foot-pound 
3,942 

work of isothermal compression, theoretical; the figure being 

from the adiabatic and isothermal columns in Table XIX. The 

actual loss may be much less in the most efficient water-jacketed 

head compressors, as shown in a comparison of columns 2 and 4 

in Table XIX. Taking the figures for 80 pounds from these 

columns we have ^'' ^ ~ 3*94 _ 20 ^ p er cent j oss j n f 00 t- 

3,942 
pounds of the work of isothermal compression. 



:8o 



COMPRESSED AIR AND ITS APPLICATIONS. 



The following table will serve to illustrate the large saving 
that it is possible to effect by compounding. This table gives 
the percentage of work lost by the heat of compression, taking 
isothermal compression, or compression without heat, as a base. 



TABLE XX. — Power Lost by One, Two, and Four Stage Compression. 



Gauge 
pressures. 



63. 

8 j. 

IOO. 
2O0. 
400. 
60O. 
800. 



One 


Two 


Four 


stage. 


stage. 


stage. 


Per cent. 


Per cent. 


Per cent 


30.OO 


13-38 


4-65 


34.OO 


15-12 


5-04 


38.00 


17.10 


8.00 


52.35 


23.20 


9.01 


68. 6o 


29.70 


12.40 


83.75 


32.65 


15.06 


90.00 


35-80 


16.74 



Gauge 
pressures. 



1,000. 



200. 



1,400. 
1,600. 
1,800. 
2,OO0. 



One 


Two 


stage. 


stage. 


Per cent 


Per cent. 


96.83 


37-00 


106.15 


40.00 


108.00 


41.60 


IIO.OO 


42,90 


116.80 


44.40 


121.70 


44- 60 



Four 

stage. 



16.90 
17-45 
17.70 
18.40 
19. 12 
20.00 



In columns 2,3, and 4 no account is taken of jacket cooling, 
it being a well-known fact among pneumatic engineers that 
water jackets, especially cylinder jackets, though useful and 
perhaps indispensable, are not efficient in cooling, especially so 
in large compressors. The volume of air is so great in propor- 
tion to the surface exposed, and the time of compression so 
short, that little or no cooling takes place, jacketed heads are 
useful auxiliaries in cooling, but it has become an accepted 
theory among engineers that compounding or stage compres- 
sion is more fertile as a means of economy than any other sys- 
tem that has yet been devised. The two and four stage figures 
in this table (columns 3 and 4), are based on reduction to atmos- 
pheric temperature 6o° F. between stages. This is an impor- 
tant condition, and in order to effect it much depends on the 
intercooler. In this device we have a case of jacket cooling 
which in practice has been found to be efficient where engineers 
specify intercoolers of proper design. While cooling between 
stages we may split the air up into thin layers and thus cool it 
efficiently in a short time, a condition not possible during com- 
pression. This splitting-up process should be done thoroughly, 
and while it adds to the cost of the plant to provide efficient 
coolers, it pays in the end. 



MULTI-STAGE AIR COMPRESSION. l8l 

Referring again to the table, we learn that when air is com- 
pressed to ioo pounds pressure per square inch in a single-stage 
compressor without cooling, the heat loss may be thirty-eight 
per cent. This condition, of course, does not exist in practice, 
except perhaps at exceedingly high speeds, as there will be 
some absorption of heat by the exposed parts of the machine. 
It is safe, however, to say that in large air compressors that 
compress in a single stage up to ioo pounds gauge pressure, 
the heat loss is thirty per cent. This, as shown in the table, 
may be cut down more than one-half by compounding or com- 
pressing in two stages, and with three stages this loss is 
brought down to eight per cent theoretically, and perhaps to 
three or five per cent in practice. As higher pressures are 
used, the gain by compounding is greater. 

The practical effect of compounding, however, does not re- 
sult in any material economy, unless the air is thoroughly 
cooled between the stages. Hot air in the cylinder of an air 
compressor means a reduction in the efficiency of the machine, 
because there is not sufficient time during the stroke to cool 
thoroughly by any available means. Water jacketing, the gener- 
ally accepted practice, does not effect thorough cooling. The 
air in the cylinder is so large in volume that but a fraction of 
its surface is brought in contact with the jacketed parts. Air 
is a bad conductor of heat and takes time to change its temper- 
ature. The piston, while pushing the air toward the head, 
rapidly drives it away from the jacketed surfaces, so that little 
or no cooling takes place. This is especially true of large 
cylinders, where the economy effected by water jackets is con- 
siderably less than in small cylinders. Leaks through the 
valves or past the piston will explain many indicator cards, 
and until something better than a water jacket is devised it is 
well to seek economy in air compression through compounding. 

In the case of high pressures, that is, from 500 to 3,000 
pounds, it is essential to resort to compounding on the most 
economic lines by water-jacketing to the furthest extent and 



I 82 



COMPRESSED AIR AND ITS APPLICATIONS. 



to intercooling to a possible normal temperature, and for from 
2,000 to 3,000 pounds the four-stage operation becomes imper- 
ative. 



Water outlet 



THE INTERCOOLER IN STAGE COMPRESSION. 

One of the most important adjuncts in the economy of com- 
pressing air by stages to any desired pressure is the intercooler. 
For its best or most economical effect upon the work of a 
compound or multi-stage compressor, it should cool the passing 

air between each of the compres- 
sion stages to its normal tempera- 
ture, and, if colder water is avail- 
able, to a temperature as much as 
possible below the normal temper- 
ature. We illustrate in Fig. 52 
one of the most approved combin- 
ations of intercooler and receiver, 
the Sergeant type, in which the 
heated air, direct from the com- 
pressor, passes into an upper 
opening, and down between a large 
number of small tinned copper 
tubes, held vertically in a sort of 
chimney. The air finally emerges 
into the shell portion of the inter- 
cooler and is free to travel through 
the top to the outlet tube. The 
smaller tubes mentioned terminate 
at either end in plates, into which they are expanded. The 
cooling water enters through the lower pipe and is forced up- 
ward through the cooler tubes, and finally emerges at the water 
outlet at the top. The water tubes are set so close together that 
they divide the incoming stream of air into thin sheets and bring 
it into very intimate contact with the cooling surface. As stated, 
the air is caused to enter at the top and pass downward, while 




Fig. 52. -the sergeant intercooler. 



MULTI-STAGE AIR COMPRESSION. 1 83 

the cooling water enters at the bottom and passes upward. 
This is the accumulating principle upon which all successful 
liquid-air apparatus have been constructed. 

A properly designed intercooler should reduce the temper- 
ature of the compressed air to its original point; that is, to the 
temperature of the intake air. It can do even more than this, 
especially in winter, when the water used in the intercooler is 
of low temperature. A simple coil of pipe submerged in water 
is not an effective intercooler, because the air passes through 
the coil too rapidly to be cooled in the core, and such inter- 
coolers do not sufficiently split up the air to enable it to be 
cooled rapidly. This splitting up of air is an important point. 
A nest of tubes carrying water and arranged as described, so 
that the air is forced between and around the tubes, is an im- 
portant point in an efficient form of intercooler. If the tubes 
are close enough together and are kept cold, the air must split 
up into thin sheets while passing through. Such devices are 
naturally expensive ; but first cost is a small item when com- 
pared with the efficiency of the compressor, measured in the 
coal and water consumed. 

Receiver-intercoolers are more efficient than those of the 
common type, because the air is given more time to pass 
through the cooling stages, and because of the freedom from 
wire-drawing in the intake of the next cylinder, which may take 
place in intercoolers of small volumetric capacity. 

See Fig. 54 for illustration of intercooler of the Rand Drill 
Co., and further on for that of the Norwalk Compressor. 

AFTERCOOLERS. 

Aftercoolers are in some installations as important as in- 
tercoolers. An aftercooler serves to reduce the temperature of 
the air after the final compression. In doing this it serves as a 
dryer, reducing the temperature of air to the dew-point, thus 
abstracting moisture before the air is started on its journey. 
In cold weather, with air pipes laid over the ground, an after- 



1 84 



COMPRESSED AIR AND ITS APPLICATIONS. 







MULTI-STAGE AIR COMPRESSION. 



I8 5 



cooler may prevent accumulation of frost in the interior walls of 
the pipes, for where the hot compressed air is allowed to cool 
gradually, the walls of the pipe in cold weather act like a sur- 
face condenser, and moisture may be deposited on the inside for 
the same reason that we have frost on the inner side of a win- 
dow pane. In using these aftercoolers, and also intercoolers, 
it is good practice to allow from 8 to 10 cubic feet of free air 









Fig. 54.— the rand intercoolek. 



per minute for each square foot of cooling surface. Further, 
an allowance of 1 pound of water for each 2 cubic feet of free 
air should be made. 

In Fig. 53 we illustrate the Ingersoll-Sergeant steam actu- 
ated " straight-line " compound air compressor with an inter- 
cooler attached directly to the top of the cylinders. The inter- 
cooling cylinder or drum contains a water-circulating coil of pipes 
around which the air passes from the low to the high pressure 
cylinder. The pipe surface being so large, the air is cooled to 



1 86 



COMPRESSED AIR AND ITS APPLICATIONS. 



its normal temperature or possibly below when cold water is 
available. 

In Fig. 54 is illustrated the intercooler of the Rand Drill 
Company, which by its form and position allows of a very large 
amount of cooling surface to be utilized in the transfer of air 
from the low to the high pressure cylinder with a minimum 
amount of retardation by friction, thus giving to a two-stage 
system of compression a high efficiency. 

One of the principal advantages of two-stage compression 
over single-stage compression is found in the reduction of loss 
due to the heat of compression, and this represents a saving in 
power, since the resistance due to compression is directly pro- 
portional to changes in temperature. Other reductions in losses 

are found in reduction of 
clearance and strains and 
in a more uniform air resist- 
ance. 





Intermediate Air Cylinder 
Scale 367 



High Pressure Air Cylinder 

scale tmo THREE-STAGE AIR COMPRES- 

SION. 

The three cards, Fig. 55, 
represent in reduced scale 
the low-pressure, interme- 
diate, and high-pressure 
cards of a three-stage com- 
pressor for compressing air 
to 2,000 pounds gauge press- 
ure for a pneumatic gun bat- 
tery at Fort Winfield Scott, 
San Francisco, Cal. The 
discharge from the low-pressure cylinder was at 75 pounds, 
intermediate at 375 pounds, and the high-pressure at 2,000 
pounds. The temperatures of the incoming air were brought 
down to slightly below normal by efficient intercoolers — the 
normal temperature being 75 F., the intermediate inlet show- 




Low Pressure Air Cylinder 
Scale iO 



-THREE- STAGE AIR COMPRESSION. 



In Fig. 57 we present a combined air card of 
four-stage compression to 2,500 pounds per square 




MULTI-STAGE AIR COMPRESSION. I 87 

ing 73 F., and the high-pressure inlet 69 F. The large area 
of the receivers seems to have been a source of economy, as 
shown in the inlet lines of the cards. The cylinders, being all 
thoroughly water- jacketed, gave the following temperatures in 
the discharge pipe: Low pressure 320 F., inter- 
mediate 289 F., high pressure 3 5 8° F., the adia- 
batic differences being ioo°, 264 , and 522 respec- 
tively. This is a most interesting showing of the 
value of proper intercooling. 

The combined card equivalent to the three cards 
Fig. 55 is shown in Fig. 56, in which the cubic feet 
per revolution is scaled at the bottom of the card 
and the pressure for each stage is shown at the 
right of the vertical leg. The delivery lines of 
these cards show a faultless arrangement of air con- 
nections and valve areas. 

FOUR-STAGE AIR COMPRESSION. 



H [T 

Cubic Feet of Air pei- Revolution 

Fig. 56.— three-stage compression card. 



inch. It represents the conditions derived from the actual 
cards taken from a four-cylinder single-acting compressor of the 
Ingersoll-Sergeant Drill Company, operated by two non-con- 
densing Corliss engines; the individual steam cards of which, 
with the air cards, are shown in Fig. 58. The steam cylinders 
were 18 by 36 inches, direct connected. 

The low and first intermediate air pistons were connected to 
one engine, the second intermediate and high-pressure air pis- 
tons to the other engine ; the engines being connected on one 



1 88 COMPRESSED AIR AND ITS APPLICATIONS. 

shaft with cranks at right angles. The four single-acting air 
cylinders were 21^, 9, 7, and 3-^ inches diameter respectively, 
by 36-inch stroke. 

All the air cylinders were water-jacketed and provided with 
intercoolers of the Ingersoll-Sergeant type. The first inter- 
cooler has a capacity of 9 cubic feet as against 7.241 cubic feet 
in the low-pressure cylinder, with a cooling surface 112 square 
feet. The second intercooler was 1.8 cubic 
feet as against 1.32 cubic feet in the first in- 
termediate, with 60 square feet of cooling 
surface. The third intercooler was .7 cubic 
foot as against .57 cubic foot in the second 
intermediate air cylinder, with 35 square 
feet of cooling surface; while the after- 
cooler was of 1.6 cubic feet capacity with 45 
square feet of cooling surface. The uniform 
lines of air intake, as shown on the separate 
cards, are of interest and are due to the 
large intercooler capacity in its relation to 
the following cylinder. For this relation we 
find that the first intercooler had 6.8 times 
the volume of the second compressing cyl- 




1.5 



Fig. 57.— four-stage air compression card. 



MULTI-STAGE AIR COMPRESSION. 1 89 

inder, and the second intercooler had 3.2 times the volume 
of the following or third compressing cylinder, while the third 
intercooler had a volume of 3.9 times that of the high-pressure 
cylinder. 

The compressor engines made 58 revolutions per minute, 
compressing 419 cubic feet of free air from atmospheric press- 
ure at 75 F. to 2,500 pounds pressure, and delivering the air 




First Intermediate At 



lull niirdinlc Air 




SEPARATE AIR CARDS AND STEAM CARDS 



from the high-pressure cylinder at 230 F., and from the after- 
cooler at normal temperature. 

The horse power developed at the maximum air pressure 
was 204 I. H. P. in the engines and 168.5 in the compressor, 
showing an efficiency of .826 for the friction losses in the 
entire plant. The temperature of the air throughout the 
stages is of interest, and from the record, the air entered the 
first stage at 74 F., was delivered at 176 , entered the second 
cylinder at 90 , was delivered at 142 , and finally delivered 
from the high-pressure cylinder at 230 F. The figures also 
show that 2 cubic feet or possibly more free air can be com- 
pressed to 2,500 pounds per square inch per indicated horse 
power. We have no test for general efficiency under full work- 
ing pressure of this four-stage compressor; but tests made 
while running from 135 to 170 atmospheres gave an efficiency 



igo COMPRESSED AIR AND ITS APPLICATIONS. 

of about 65 per cent, and from the work of filling the receivers 
from 1 to 171 atmospheres, an average efficiency of 68 per cent; 
so that in regular work at full load the efficiency may be antici- 
pated to average about 63 per cent. 

In tests made by representatives from the Cornell Uni- 
versity, the several efficiencies of the apparatus are given as 
follows: Mechanical efficiency, 90.4 per cent; efficiency of com- 
pression, 88.9 per cent; volumetric efficiency, 89.34 per cent. 
The product of these is 71.8 per cent, a considerably higher fig- 
ure than either of those obtained from calculations based on the 
receiver pressure. We are unable to account for the difference 
except on the supposition that the indicated work of the air 
cylinders was not accurately measured. All indicator cards are 
liable to certain percentages of error, and there is an unusually 
large probability of error in the measurement of the indicated 
work in the second intermediate and the high-pressure air 
cylinders, since the pistons of the indicators used in taking the 
cards were only of }( and 0.1 inch diameter, respectively; and 
the nominal scale of the springs was, respectively, 250 and 
1,250 pounds to the inch. 

The method of computing the efficiency of the apparatus by 
comparing directly the work done in the steam cylinders with 
the work of storing the air in the receiver, measured by the 
volume of the receiver and the difference between the pressure 
at the beginning and end of the test, eliminates the errors of 
measuring the work done in the air cylinders by means of indi- 
cator diagrams. By this method it is not at all necessary to 
take diagrams from the air cylinders, although such diagrams 
are valuable for determining approximately the proportions of 
work done in the several cylinders, the value of the water 
jackets and intercoolers in reducing the total work of com- 
pression, the mechanical efficiency of the apparatus, and the 
so-called efficiency of compression, or the ratio of the indicated 
work in the air cylinders to the theoretical work of isothermal 
compression. 



MULTI-STAGE AIR COMPRESSION. 191 

It is fair to state that the efficiency obtained above is based 
on tests made when the plant was newly set up and running 
under conditions in some respects less favorable than those 
which may obtain when it has been longer in service. Con- 
sidering this fact and the very high pressure to which the air is 
raised, the figures of efficiency above attained appear very 
creditable to the designers and builders of this remarkable 
compressor. 

THE FOOT-POUND WORK OF MULTIPLE-STAGE AIR 
COMPRESSION. 

Using the following formulas, we have for the first stage, 
and for the second stage, 



W 

y 



•^(s^ws— o ( -> 



when the air is cooled to normal temperature between the 
stages, and for computation, P = 2,116.8, the pressure of the 
free atmosphere per square foot. V = 1 cubic foot or any 

number of cubic feet. — ±- — = — — = 3.438. t- = the 
y — 1 .406 P 

logarithmic ratio of the normal and the assumed absolute pres- 
sure of compression. _ = — ^ — = .29. — 1 and — 2 are 

y 1.406 

the integers of the index of the logarithmic product of the 
pressure ratio and its exponent. 

For a two-stage compression to 100 pounds gauge pressure 
and to 50 pounds for the first stage, the computation is as fol- 
lows : 

First stage, 2,1 16.8 X 1 X 3.438 = 7,277.55. 2 = -iiZ = 

P 14.7 

4.401 the ratio; the logarithm of which is 0.64355 1 X by the ex- 
ponent .29 = o. 186629, the index of which = 1.537— 1 = • 537> 
which X 7,277.55 = 3,908 foot-pounds per cubic foot. To this 



i 9 : 



COMPRESSED AIR AND ITS APPLICATIONS. 



should be added the compressor friction and deducted the value 
in foot-pounds of the cooling effect of the cylinder. 

For the second stage we have 2, 1 16.8 X 1 X 3.438 = 7,277.55 
as before and the index of the first compression logarithm 1.537, 
to which must be added the index of the log. of the ratio of the 
P. ._ 1147 



second stage, which is £- 



64.7 



= 1.7727 = log. 0.24861 X 



.29 = 0.072097, the index of which is 1. 181, to which add the 
index of the first stage 1.537 = 2.718, and 2.718 — 2 = .718 X 
7,277. 5 5 = 5,228 foot-pounds per cubic foot, and .158 of a horse 
power per cubic foot, to which should be added the compressor 
friction, say 5 per cent, and deduct for cylinder cooling, say 8 
per cent, which will be about 3 per cent to be deducted ; or the 
theoretical work will nearly cover the losses and gains. 

TABLE XXI. — Horse-Power Developed to Compress 100 Cubic Feet of 
Free Air. from Atmosphere to Various Pressures. 



Gauge pressure, 
pounds. 


One-stage 

compression 

D. H. P. 


Gauge pressure, 
pounds. 


Two-stage 

compression 

D. H. P. 


Four-stage 

compression 

D. H. P. 




3.60 
5-03 
6.28 
7.42 
S.47 
9.42 
10.30 
11. 14 
11.90 
12.07 
I3-4I 
14.72 
15-94 
17.06 
18.15 


6o 


II.70 

13-70 
15-40 
21.20 
24.50 
27.70 
29-75 
31.70 
33-5o 
34-90 
36.30 
37.S0 
39-7o 
43.00 
45-5o 






80 


12.50 
14.20 

18.75 
2I.8o 


















24.OO 
25-90 
27-50 
28.90 
30.00 
31.OO 
31.80 
33-30 
35-65 
37.S0 
39.06 
40.15 






45 

50 


600 ... 


55 


800 


6j . . 








80 

























For a three-stage compression to, say, 1,000 pounds gauge 
pressure, we have from the value of the first three terms as be- 
fore 7,277.55 X by the sum of the indices for the logarithms of 
the ratios for each previous stage -j- the index of the last stage 
— 3, the integers for three stages. The third stage will be 



114.7 



8,846 log. 0.946747 X .29 = 0.274556, index 



MULTI-STAGE AIR COMPRESSION. I93 

i. 8815 + 2.718 == 4-5995 — 3 = 1-5995 X 7,277.55 = 11, 640 foot- 
pounds per cubic foot, or .352 of a horse power per cubic foot. 

The compression of 100 cubic feet of free air per minute and 
the work developed in horse power has been tabulated from the 
formulas before given for one, two, and four stage compression. 
It represents very nearly the actual work of compression in first- 
class compressors, allowing for cylinder cooling, intercooling, 
and friction, which last partially neutralizes the cylinder-cooling 
effect. Table XXI. 

The economy in power saved by two-stage compression for 
even as low a pressure as 60 pounds is very evident by inspec- 
tion of this table, which shows for sixty pounds a saving of 14.5 
per cent and for 100 pounds 17.8 per cent. The saving for 
1,000 pounds pressure of a four-stage compression over a two- 
stage is 18.8 per cent. 
13 



Chapter XIII. 



THE EXPANSION OF 

COMPRESSED AIR AND THE 

WORK OF THE MOTOR 



THE EXPANSION OF COMPRESSED AIR AND THE 
WORK OF THE MOTOR. 

The expansion of compressed air does work in a cylinder on 
the same lines as in the work of compression. The curve of 
expansion from normal temperature for compressed air is adi- 
abatic in the negative sense, for by compression the pressure 
and work are cumulative, while by expansion they are depletive, 




Fig. 59.— expansion card. 

as shown by the card Fig. 59, in which the three radial lines of air 
pressure and work are shown. The curves are all hyperbolic 
in form, and for expansion are subject to an inversion of the 
equations and formulas used in compression. The theoretical 
equations for the expansion of air when no heat is absorbed 
by the motor cylinder are the same as for compression with 
the principal terms inverted. Therefore the 1.406 powers of 
the specific volumes are inversely proportional to the corre- 
sponding absolute pressures and temperatures. 



I98 COMPRESSED AIR AND ITS APPLICATIONS. 

We have then the proportion v 1A0B : v, I40C : : p : : p and 
p v 1 - 40r ' = p, v, 1 - 406 v, and p, being the greater volume and press- 
Then using logarithms, 1.406 X log. — 



v 



P 



= log. ±-i and log. -£ = 1.406 X log. — \ or 

PP. v P. 

If we assume the initial volume v, = 1, and the original ten- 
sion or pressure p, = 1 atmosphere, we have for the pressure 
or tension p when the air has expanded to twice its volume, or 

v = 2 Vj, without loss of heat (adiabatic), 1 .406 X log. 2 = log. 

P 
Then, for example, 1.406 X log. 0.30103 = log. 0.423248 = log. 

-. Then log. 0.423248 index = 2.65 and — = = .377 at- 

p p 2.65 

mosphere. 

For temperature of expansion we have, 

'v \°' 4 " 6 _ T, _ absolute reduced temperature 



G 



,v,/ T absolute normal temperature 

Then for a specific volume v, expanded to 2 volumes from a 

(2 v \ 0.406 
/ = 

4 — i and log. 2 = 0.30103 X 0.406 = log. 0.1222 18, index 

462 -f t 

1.325 = the ratio of the respective temperatures. Then 522 X 
1.325 = 691.6 — 522 = 169. 6°, the drop in temperature due to 
the expansion of one volume to two volumes from 6o° F. For 
the terminal pressure from the adiabatic expansion of com- 
pressed air in an engine or motor cylinder, we have the formula 

P_ 

P = terminal pressure, 
R 

in which p is the absolute initial pressure or gauge pressure 
plus 14.7, and P the absolute atmospheric pressure, 14.7. 

— = the ratio of expansion obtained by dividing 1 by the cut-off 
expressed in tenths of the stroke of the piston. Thus for a cut- 
off of A or. 3, — = 3.333 the ratio, the logarithm of which must 
10 3 



m 



THE EXPANSION OF COMPRESSED AIR. 1 99 

be multiplied by the exponent 1.406. The index of the loga- 
rithmic product becomes a divisor of the absolute initial press- 
ure, from the quotient of which the atmospheric pressure must 

be deducted for the terminal pressure. For example, for — 

10 

cut-off and 60 pounds gauge pressure, we have — =3.333 log. 

3 

0.522835 X 1.406 = 0.735 106, the index of which is 5.434; then 

ZziL = 13.7 — 14.7= —1. The terminal pressure being one 
5-434 

pound less than atmospheric pressure. 

By a series of terminal pressures computed by the above 
formula, a card may be made indicating the terminal pressures 
of the adiabatic curve for any number of divisions so arranged 
that the cut-off may represent an even number of divisions, and 
the sum of all the divisions divided by the number will equal 
the mean pressure. 

As an example we illustrate this method by a card Fig. 60 

detailed for — cut-off at 100 pounds gauge pressure. 
10 

The approximate mean of the expansion from the third to 

the fourth division will be as follows : The ratio of expansion 

for the terminal is - = 1 .333 log. o. 12483 X 1.406=0.17551, 
3 

., n mi 11 4- 7 ^ -^ ^o , 6i.8 4- 100 

index 1.498. Then — -Li = 76.56 — 14.7 = 61.8 and ! . 

1.498 2 

= 80.9 the mean pressure due to the expansion of the fourth space. 

The next terminal will be — = 1.666 log. 0.221675 X 1.406 = 

3 

0.311675, index 2.05, and — — =55.9—14.7 = 41.2. Then 

2.05 

4_ : L '— = 51.5 the mean pressure of the fifth space, and so 



on through the ten spaces; the whole aggregating 



527-94 = 
10 

52.79, the mean pressure of the card with a terminal of 6.58 

pounds, which approximates nearly to the figures given as 



200 



COMPRESSED AIR AND ITS APPLICATIONS. 



computed from the ratios in the 3d and 7th columns of Table 
XXIII. These computations and the values given in Table 
XXIII. are theoretical, and take no account of the clearance in 
the cylinder and ports and of the absorption of heat by the air 
from the motor cylinder. It is noted that the cylinder of a 
motor is much colder than the outer air when compressed air at 
atmospheric temperature is used, and heat is being constantly 
absorbed by the cylinder and given to the expanding air. It 
will be readily understood that the walls of a motor cylinder, 

as soon as normal running con- 

SH7.M 

ditions are established, absorb heat 
from the incoming air at atmos- 
pheric temperature until a moment 
after the cut-off, when the con- 
dition becomes reversed and the 
cold expanding air receives heat 
from the walls of the cylinder in 
an increasing degree until the ex- 
haust takes place, when, if under 
a terminal pressure, the tempera- 
ture of the contents of the cylinder suddenly drops to the point 
due to the total expansion from the working pressure to atmos- 
pheric pressure, less the amount of heat absorbed at full press- 
ure or given to the expanding air during the expulsion of the 
cold air on the return stroke of the piston. These amounts 
are small in their effect upon motor efficiency, and can be entirely 
eliminated by warming the motor cylinder — just the opposite of 
the treatment of a compressor cylinder for increasing its effi- 
ciency. The clearance in a motor cylinder adds to its mean 
pressure at the expense of the relative volume of the stroke at 
the cut-off. The volume of the clearance also increases the vol- 
ume due to the nominal cut-off, varying with the cut-off volume. 
In the following table is given the actual cut-off due to the 
various percentages of the clearance in motor cylinders for the 
nominal cut-off as given in column 1. 




*-li,7-> 6 - ss 

Fig. 60.— expansion card 



THE EXPANSION OF COMPRESSED AIR. 201 

For example, let the cylinder stroke be 10 and the clearance 

.07 per cent, cut-off —, then 10 X .07 = .7 -j- 10 = 10.7, the 
10 

actual volume of cylinder and clearance. Then the sum of the 
ratios of the cut-off and clearance divided by the actual vol- 
ume of the cylinder and clearance equals the actual clearance, 

3 +-7 = -^- = -3457 the actual clearance. In this manner 
10.7 

the following table of nominal cut-off percentage of clearance 

and actual cut-off has been computed. The rule serves for any 

cut-off and clearance. 

TABLE XXII.— Excess of Cut-Off Due to the Percentage of Clearance 
for the Nominal Cut-Off in Column i, for Compressed-Air Motors. 



Nominal cut-off. 



0. 10 
.12 
.14 
.16 
.18 
.20 
.22 
.24 
•25 
.26 
.28 
•30 
.32 

• 34 
.36 

.38 
.40 
.42 

• 44 
.46 
.48 
.50 
.52 

• 54 

• 56 
.58 
.60 
.62 
.64 
.66 
.68 
.70 
.72 
•74 

• 75 



Percentage of Clearanci 



•°3 



126 

146 
165 

184 

204 

223 
243 

262 
272 

281 
301 
320 
340 

359 
378 
398 
417 
437 
456 
475 
495 
5^4 
534 
554 
573 
593 
612 
632 
651 
670 
690 
709 
729 
748 
758 



.04 



O.I35 

• 154 
.174 

• 193 
.212 
.231 
•251 
.270 
•279 
.289 
.308 
•327 
•346 
.366 
.385 
.404 
•423 
.442 
.462 
.481 
.500 
.519 
.538 

• 558 
•577 

• 596 
.615 
•634 

• 654 
•673 
.692 
.711 
•731 
.750 
.760 



O.I43 
162 
181 
200 
219 
238 
257 
276 
286 
295 
314 
333 
352 
371 
390 
409 
429 
448 
467 
486 
505 
524 
543 
562 
58i 
600 
619 
638 
657 
676 
695 
714 
733 
752 
762 



0.151 
170 
189 

207 
226 

245 
264 
283 
293 
302 
321 
34o 
359 
37S 
396 
4i5 
434 
453 
472 
490 
509 
52S 
547 
566 
5S5 
604 
623 
642 
661 
679 
698 
717 
736 
755 
764 



.07 



0.159 
.177 
.196 
.215 

• 233 
.252 
.271 
.290 
•299 
.308 

• 327 
■ 346 
■364 

• 383 
.402 
.420 
•439 

• 458 
•477 
•495 
.514 
•533 

• 551 

• 570 
.589 
.607 
.626 
•645 
.664 
.682 
.701 
.720 
.738 

• 757 
.766 



0.167 
185 
.204 
,222 
.240 
.259 
,277 
.296 
305 

• 315 
•333 
■ 352 

• 37o 
.389 
.407 

• 425 
•444 
.462 

481 
500 
518 
537 
555 
574 
593 
611 
630 
648 
667 
685 
703 
722 
74o 
759 
768 



0.182 
.200 
.218 
.236 
•254 
•273 
.291 
•309 
.318 
•327 
•345 
•364 
.382 
.400 
.418 
•436 
•455 
•473 
.491 
■ 509 
• 527 
.546 
•564 
.582 
.600 
.618 
•637 
.655 
•673 
.691 
■709 
.727 
■745 
•763 
.772 



202 COMPRESSED AIR AND ITS APPLICATIONS. 

In Table XXIII. are given the theoretical conditions in re- 
gard to the pressures and temperatures of compressed air when 
expanding in the cylinder of a motor engine, to which correc- 
tions must be made for clearance by adding the additional 
amount to the cut-off as per Table XXII. for various percent- 
ages of clearance, for a definite ratio of expansion, from which 
other ratios for the pressures and temperatures may be com- 
puted from the formulas given for each column in Table XXIII. 



TABLE XXIII. — Ratios of Pressures and Temperatures due to Expansion 
of Compressed Air in a Motor Cylinder, Theoretical. 





o 


a 


«8 ft" 




cut-off. 
Ratio of mean 


j II 

52 l 

»i-B 

I 0) cc 
J ft* 
' X 
> CM 


ft 


Ratio of 

mean to total 

absolute 

pressure during 

expansion onlv. 

P X Ratio - P". 


Ratio of 
initial to final 
temperature. 

absolute 

temperature of 

exhaust. 

Ratio of initial 


temperature 
due to cylinder 
expansion only. 

TXR = T,. 

Ratio of 
initial to final 


pressures for 

ratio of 

expansion. 

P x R - P = 

final pressure. 


I 


2 


3 


4 


5 


6 


7 


O. IO 


10.00 


2493 


0.1659 


0.3908 


5131 


0391 




12 


8.33 


29 3 




1935 




4210 


54io 


0505 




14 


7-14 


3293 




2201 




4484 


5657 


0628 




16 


6.25 


3665 




2458 




4735 


5880 


0758 




18 


5-55 


4020 




2708 




4968 


6084 


0894 




20 


5. GO 


4360 




2950 




5186 


6273 


1037 




22 


4-54 


4685 




3186 




5392 


6448 


1186 




24 


4.16 


4996 




3416 




5586 


6613 


1341 




25 


4.00 


5147 




3529 




5680 


6692 


1420 




26 


3-84 


5295 




3641 




5772 


676S 


1501 




28 


3-57 


558o 




3861 




5949 


6915 


1666 




30 


3-33 


5S54 




4077 




6119 


7055 


1836 




32 


3.12 


6116 




4288 




6282 


7188 


2010 




34 


2.94 


6367 




4496 




6439 


73i5 


2189 




36 


2.78 


6608 




47-o 




6591 


7438 


2373 




38 


2.63 


68 3 S 




4900 




6738 


7565 


2561 




40 


2.50 


7 58 




5097 




6881 


7668 


2752 




42 


2.38 


7269 




5291 




7019 


7777 


2948 




44 


2.27 


7470 




5481 




7154 


7883 


3148 




46 


2.17 


7662 




5670 




7285 


7985 


335i 




48 


2.08 


7S45 




5855 




7412 


8084 


3558 




50 


2.00 


8019 




6338 




7537 


8180 


3768 




52 


1.92 


8185 




6218 




7658 


8274 


3982 




54 


1.85 


8342 




6396 




7777 


8365 


4200 




56 


1.78 


8492 




6572 




7893 


8453 


4420 




58 


1.72 


8633 




6745 




8007 


8540 


4644 




60 


1.667 


8767 




6919 




8119 


8624 


4871 




62 


1. 61 


8893 




7.86 




8228 


87-6 


5101 




64 


1.56 


9 )ii 




7254 




8335 


8787 


5335 




66 


1. 51 


9123 




74i9 




8441 


8866 


557i 




68 


1.47 


9227 




7583 




8544 


8943 


5810 




70 


1.429 


9324 




7745 




8646 


9018 


6052 




72 


i-39 


9414 




79 6 




8746 


9092 


6297 




74 


i-35 


9497 




8,64 




8844 


9 l6 5 


6545 


• 75 


1-333 


9536 


.8143 


.8893 


9200 


6669 



THE EXPANSION OF COMPRESSED AIR. 203 

In these columns R is the ratio as in column 2, or a ratio as- 
sumed by the addition for clearance percentage as given in 
Table XXII. Account should be taken of the heat absorbed 
by a motor cylinder when operated by compressed air at atmos- 
pheric temperature. When air is reheated before entering a 
motor cylinder so as to exhaust at near atmospheric temper- 
ature, the theoretical conditions will not be materially affected. 
The formulas from which Table XXIII. has been computed 
are: 

For column 2, = ratio of expansion. 

cut-off r 

2.45 1 X [.-(£f , 

For column 3, the formula is ^ ~^T> = 

ratio of mean pressure during the whole stroke, and (p X ratio) 
— P = mean pressure. The first terms of the equation as shown 

below become '9-> "33 _ .2854, adding — = .3 =. 5854 the ra- 

3-333 R 

tio for .3 cut-off as in column 3. 

2.451 x [,- (i)"" 

For column 4, p— = ratio of mean to total 

absolute pressure during expansion only ; for which the value 
is obtained by multiplying the absolute initial pressure by the 
ratio and subtracting the atmospheric pressure, p X ratio — 
P = mean pressure. As an example, for computing from this 
formula, we assume a motor running with 50 pounds gauge 

pressure and — cut-off. The formula may then be written 
10 



2.451 X [1 - 



3-33 - 1 
The exponential ratio must be obtained by logarithms. 
Log. 3.333 = 0.522835 X .408 = log. 0.213316 index of which 

is 1.634 and = .6119 and 1 -- .61 19 = .3881 X 2.45 1 — 

1.634 

.9512331 and '22 — ±L_ = .4077, the ratio as found in column 4. 
2-333 



204 COMPRESSED AIR AND ITS APPLICATIONS. 

/ I Y 408 ^ 
Column 5. /— J the ratio being for — cut-off 3.333 as be- 
fore, log. X by the exponent gives = .6119, as found in 

1.634 

column 5. Then if a motor is running with 50 pounds gauge 
pressure and at 6o° F. atmospheric temperature, or 520 abso- 
lute, and (520 X .6119) — 460 = — 142 F. theoretical, modified 
by the effect of the clearance and heat absorbed from the outer 
atmosphere through the cylinder. In this case the final press- 
ure at exhaust as per ratio in column 7 will be 64.7 X .1836 = 

11.87— l 4-7 — —2-83 pounds, which shows that a A cut-off is 

10 

not the most economical point unless the clearance is sufficient 
to bring the final pressure to the atmospheric line or enough 
above to compensate for engine friction. 

Column 6. (~\ is the ratio of temperature for initial and 

final pressures, and is obtained by the same method as for 
column 5. 

Then for — cut-off as above (520 X .7055) — 460 = — 93. 2 ; 

the temperature when the pressure reaches the atmospheric 
line. 

Column 7. \R/ is the ratio of initial and final absolute 

1 \ ■ 408 

pressures for the given ratio of volume (— ) which is the 

logarithmic ratio as in column 5, divided by the ratio in column 
2, and gives the terminal pressure in the cylinder; as, for ex- 
ample, for 50 pounds gauge pressure and A cut-off (64.7 X 

10 

.1836) — 14.7 = — 2.83 or nearly 3 pounds negative pressure. 

Now, for example, take the clearance effect into consider- 
ation for the same pressure and cut-off. We find that for a 
clearance of 5 per cent the nominal cut-off will be advanced to 

(if 

a real cut-off of .333 and = 3 the ratio. Then V 3 / 

•333 ■ 

3 



THE EXPANSION OF COMPRESSED AIR. 



205 



log. .477121 X .408 = 0.194665, index of which is 1.565 and 

= .639 and '—±* = .213, the ratio of the absolute initial 

1-565 3 

and final pressures. Then (64.7 X .213) — 14.7 = — 1, the 
terminal pressure. 

Thus we find that at 60 pounds gauge pressure — cut-off 

with 5 per cent clearance will give a terminal pressure of + 1.2 
pounds, which is a very economical point of cut-off for this 
pressure and clearance. 

TABLE XXIV. — Mean and Terminal Pressures in an Air Engine or 
Motor. Theoretical and Not Including Clearance. With Ratios for 
Each Cut-Off. 






Pressures. 


Gauge Pressures, Pounds. 


Ratio. 


3 



5°- 


60. 


70. 


So. 


90. 


100. 


PXR-P. 


*{ 


Mean 

Terminal . . 


13-5 
- 8.0 


17.8 
- 7.0 


22.2 
- 6.0 


26.5 
- 4.9 


30.9 
- 3-9 


35-3 
- 2.8 


O.4360 
•I037 


1 1 

* < 


Mean 

Terminal . . 


18.6 

- 5-6 


23-7 
- 4-i 


28.9 
2.7 


34-o 
- 1-3 


39-2 

+ •1 


44-3 
1.6 


•5147 
.1420 


3 j 

To | 


Mean 

Terminal . . 


23.2 
- 2.6 


29.0 
— 1.0 


34-9 

+ .8 


40.7 
2.6 


46.6 
4-5 


52.4 
6.3 


.5854 
.1836 


AVJ 


Mean 

Terminal . . 


28.0 
0.0 


34-7 
2-3 


41.2 
4.6 


47-8 
6.9 


54-5 
9.2 


61.0 
". 5 


.6608 
.2281 


4 i 

TO, 


Mean 

Terminal . . 


31.0 
3-i 


38.0 

5-8 


45-i 
8.6 


52.1 
11. 4 


59-3 
14. 1 


66.3 
16.9 


.7058 
.2752 


5 j 
10 \ 


Mean 

Terminal . . 


37-2 
9.6 


45-2 
13-4 


53-2 
17.2 


61.2 
21.0 


69.2 
24.7 


77-3 
28.5 

85.9 
41.2 


.8019 
..3768 


6 i 


Mean 

Terminal . . 


42.0 
16.8 


50.8 
21.7 


59-5 
26.5 


68.3 

3i-4 


77-1 
36-3 


.8767 

.4871 



The values in the above table are derived from the ratios in 
Table XXIII. and may be interpolated by using ratios in that 
table, or the formula by which they were computed for any re- 
quired cut-off, to which the extensions for any percentage of 
clearance may be added from Table XXII. 



»o6 COMPRESSED AIR AND ITS APPLICATIONS. 



THE WORK OF EXPANSION. 

The work of expansion of air from any temperature to the 
zero of absolute temperature in foot-pounds has an intrinsic 
value measured by the mechanical equivalent of air at constant 
volume, Mcv, = 778 X .1689 = 131. 6 foot-pounds per unit of 
heat. Then from 6o° F. the absolute temperature is 520 F., 
and 520 X 131.6 = 68,432 foot-pounds. 

From 32 F. it is 492 X 13 1.6 = 64,747 foot-pounds. 

By another formula, the atmospheric pressure P multiplied 
by the volume of 1 pound of air in cubic feet at atmospheric press- 
ure at any specific temperature, and the product divided by the 

P V 

ratio of the specific heats. — 1, or — — - for the above temper- 

.406 

ature, the work will then be — ^L_ — 68,300 foot- 

.406 
pounds. 

In Table XV. are given the volumes of 1 pound of air at vari- 
ous temperatures. The variation in the values of the specific 
heat of air at constant pressure and at constant volume, as- 
signed by different investigators, is the cause of the discrepancy 
in the results from the formulas of different authors ; see article 
on specific heat and Table XIV. 

For ascertaining the amount of foot-pound work of com- 
pressed air, expanding to atmospheric pressure from any initial 

7. T P r 

pressure, we have the formula, ° — - 

w t L \p 

pounds of work per pound of air, adiabatic expansion. 

For example, one pound of air at 2 atmospheres 29.4 pounds 

absolute pressure, 14.7 pounds gauge pressure, at 6o° F., is 

computed from the following figured terms : 

2,116.8 



3TP f, /PU 1=foot . 



3 X 520" X 



.0807 X 49 



2 L 1 (29.4/J 



83,179 x i- 3 j/- = — — = .788 

2 I.2599 



THE EXPANSION OF COMPRESSED AIR. 207 

1 — .788 = .2i2 X 83, 179 = 17,634 foot-pounds, and I ?' 34 = 

1.3- 1 
1,346 foot-pounds per cubic foot. 

For any other pressure, say 50 pound-gauge pressure. The 

sum of the first three terms is a constant, viz., 83,189, and the 

fourth term will be 

and 1 — .609 = .391 X 83,189 = 32,526.9 foot-pounds per 
pound of air expanded from 50 pounds gauge pressure to at- 
mospheric pressure. Then 1— !-5 — '-2 — 2,483 foot-pounds per 

cubic foot. 

The ratios of pressures and volumes from adiabatic com- 
pression and expansion may be obtained from the following 

formulas, — — 7 — ) and — — (— ' ) in which P, and v, are 
p Vv,/ v, Vp/ 

the greater pressures and volumes. Then, for example, for the 
relative volume of compression, say for two atmospheres abso- 
lute or any number of pounds absolute pressure, we have 

— ! — ( -ZlZ ) = [ _ ) log. 2 = 0.30103 X .71 =0.21373, the in- 

p V29.4/ \2/ 

dex of which is 1.636 and = .617, the ratio of compression 

1.636 

and expansion. Then assuming 1 pound of air 13. 1 c 1 , we have 

13. 1 X .617 = 8.08 cubic feet, the volume of 1 pound after adia- 

batic compression to 14.7 pounds gauge pressure, and -^— = 

.617 

21.2 cubic feet, the volume of 13. 1 cubic feet of air at 14.7 
pounds gauge pressure when completely expanded adiabatically 
from 14.7 pounds gauge pressure. 

The formulas for the work of expansion vary slightly in 
their results as given by different authors. Using Professor 
Unwin's formula for foot-pounds of work (theoretical) for one 
pound of air, we have 

-^Pv [1 - (|-)^] = 3-438 X 2,116.8 X13.1 = 95,336 



208 COMPRESSED AIR AND ITS APPLICATIONS. 

for the first three terms,, and for an expansion from 3 absolute 
atmospheres 44.1, to atmospheric pressure 14.7, 

[-0*]-^ [-(ir) 

Then —log. 3 = 0.477121 X .29 = log. 0.138365, the index of 
3 

which is 1.375 and = .7272, and 1 — .7272 = .2728 X 

1.375 

95,336 = 26,007 foot-pounds for the work of one pound (13. 1 
cubic feet) of air expanding from 29.4 gauge pressure to atmos- 
pheric pressure ; not including friction and lost work from 
leakage. 

Another formula from Church's "Mechanics of Engineer- 
ing," for the foot-pounds of expansion of 1 pound of free air 
compressed and used for work in a cylinder, is : 

■x T ■ — 1 — ( — Y I » in which the cube root of the press- 

.0807 1 L Vp/ J 

ure ratio is used as the exponent. Then for 30 pounds gauge 

"P 1/17 

pressure and — = — ^ , T = absolute temperature of the work- 

P 44-7 
ing air, say 6o° F., and t the absolute temperature of 32 F.. 
The figures will then be 

2,116.8 r /14. 7\Jrl 

3 x 520 x — — h 1 — [-^-r • 

.0807 x 492 L V44.7/ J 
The product of the first three terms is 83,179 X 3 y — 

— I — = .6905, and 1 — .6905 = .3095. Then 83,179 X .3095 = 
1.448 

25,743 foot-pounds, the work of expansion of one pound of free 

air (13. 1 cubic feet) at 6o° F. from 30 pounds gauge pressure to 

atmospheric pressure. ->>743 _ ^65 foot-pounds per cubic 
foot. 

In computing the practical work of expansion in a cylinder, 
the actual ratio of expansion is not due to the nominal ratio of 
the cut-off to the stroke, since expansion also takes place in the 
volume of the clearance by the amount of the piston clearance 



THE EXPANSION OF COMPRESSED AIR. 209 

and port area. As the nominal clearance is expressed in parts 
of 10, the percentage of the clearance is also expressed in parts 
of 10. Then the cut-off plus the clearance, divided by the 
cylinder volume plus the clearance, equals the actual cut-off, 
as per Tables XXII. and XXIII. and examples in their expla- 
nation. 

14 



Chapter XIV. 



TRANSMISSION OF POWER 
BY COMPRESSED AIR 



TRANSMISSION OF POWER BY COMPRESSED AIR. 

The use of compressed air for power purposes at a distance 
from the compressing plant is no longer a mooted subject of 
discussion. Successful use for even great distances has be- 
come a fact in practice, and its economy is no longer in doubt. 
More than twenty years ago the distribution of compressed air 
for power rental attracted attention, since which time it has made 
rapid strides in useful installations that are widespread ; not 
only for public service, but for operating machines and tools 
in machine shops, factories, and our great constructive works. 

For mining and drifting in tunnel work the transmission of 
compressed air for running drills and pumps has been long 
known as the leading method and the only safe and economical 
means of operating machinery underground and throughout the 
drifts and galleries to the deep headings of the modern mining 
system. 

The conveying of compressed air for a few thousand feet 
had been long in use, and its convenience and economy could 
not be gainsaid; but when transmission for miles came to be 
considered, the question of loss of power had its period of dis- 
cussion ; now the doubts raised have been put to flight by the 
later practice and its accomplished facts. 

The continuous compressed air line of ten and twenty miles 
has at last become an actuality, owing to the progress of 
manufacture of large pipe lines of great sustaining power, by 
which air at high pressure may be conveyed through pipe lines 
of suitable size to guarantee small loss from air friction. The 
apparent loss by friction may be slightly compensated by ex- 
pansion of the volume at a lower delivery pressure, so that 
what it loses in pressure it gains in value ; yet the fall in press- 
ure in long pipe lines does involve a loss in transmission, as 



214 COMPRESSED AIR AND ITS APPLICATIONS. 

shown by the loss of efficiency in the motor due to loss of ini- 
tial pressure. 

As compared with other means of transmitting power for 
great distances, air is always available and can be discharged 
from motors or pumps with a health-giving property in mines 
or in factories; it has peculiar advantages in underground work. 

The success in the distribution of compressed air for power 
and refrigeration during the past twenty years in Paris, France, 
and later in England, Switzerland, and Germany, has set aside 
all doubts as to its utility and economy. For its work in a great 
city, it has no equal, as shown by the multiplicity of operations 
carried on in Paris by the compressed-air system as lately de- 
veloped there. The compressed-air plant has now been in- 
creased to 24,000 horse power, having main pipe and distribut- 
ing lines aggregating 140 miles in length, of which about 100 
miles are used for power purposes alone, and 40 miles for the 
operation of pneumatic clocks. From the power mains the 
smaller distributing mains aggregate 20 miles in length, and 
supply 955 power consumers, and also 1,637 establishments 
in which compressed air is used for the operation of pneumatic 
clocks, of which there are about 7,000. Not only is compressed 
air used for small factory power and refrigeration, but it has 
become a most convenient power for elevators, for there are 
nearly two hundred passenger and freight elevators used 
throughout the mercantile district in which the air pipes are 
laid. A more detailed description of this interesting plant will 
be given further on. 

It is truly strange, in view of the successful operation of a 
public supply of compressed air in Paris and other parts of 
Europe for the past twenty years, that our otherwise enterpris- 
ing American cities, so noted for internal improvements, are still 
behind the age in the distribution of air power from central 
plants. 

As to the loss of power by transmission through long lines, 
the tests made with the Paris plant have furnished us with the 



TRANSMISSION OF POWER BY COMPRESSED AIR. 215 

best practical results. The average velocity in the mains of 
the Paris system for a length of main equal to 55,000 feet — 
about 10 miles — was found to be 20 feet per second, and the 
loss due to friction was 1.65 pound per mile. This for 10 
miles would amount to 16.4 pounds loss in pressure, or about 
18 per cent from an initial pressure of 92 pounds. This leaves 
a clean working pressure of 75 pounds at the end of the line, 
with higher pressures all along the line in a municipal dis- 
tribution with one continuous pipe line. In the system of dis- 
tribution as arranged in the Paris and Birmingham air plants, 
the drop in air pressure throughout the lines does not exceed 8 
pounds. 

In the planning of a compressed-air transmission system, 
especially for public service, a consideration of future wants in 
the first installation, by the laying of much larger-sized pipes 
than are required for present use, becomes a source of immedi- 
ate economy in air-pressure loss, and will obviate some of the 
troubles and losses that are now felt in the Paris plants, which 
have been caused by the increased demand for air power when 
its convenience came to be recognized by the community. To 
summarize, air is in practice proving to be a fairly cheap and 
most convenient transmitter of power, allowing fine subdivi- 
sion and transportation to remote points, with the crowning and 
unique quality of suffering no appreciable loss when held in 
storage. For intermittent service it is of great value, allowing 
widely varying speed of tools, dispensing with long lines of 
shafting and belts, giving free head-room, and increasing the 
shop-light as well as lessening the first cost of roof frames when 
they have not to carry shafting. The pipes require no coating ; 
they radiate no heat, and therefore can be put in close corners 
without increasing the fire risk ; their direction is readily 
changed in any plane without risk of pocketing or water-ham- 
mer, and leaky joints are not a nuisance or risk. In no case 
are exhaust pipes required, and in most, if not all cases, the 
exhaust adds to the men's comfort, 



2l6 COMPRESSED AIR AND ITS APPLICATIONS. 



COMPRESSED AIR FLOWING IN PIPES. 

When compressed air flows along a pipe there is necessarily 
a fall of pressure due to the resistance of the wall surface of the 
pipe, friction, and consequently the volume and velocity of 
the air increase along the length of the pipe in the direction of 
the motion. Generally, in compressed-air transmitting systems, 
the air is delivered into the mains at a temperature above that 
of the surrounding air, or of the earth in underground lines. 
The excess of heat is soon absorbed by the surrounding medium, 
and in long lines the transmission may be said to be isothermal. 
The loss of pressure is independent of any changes in 
temperature; it is directly proportional to the length of the 
pipe line and to the square of the velocity, and inversely as the 
diameter of the pipe. The gain in free air delivery by loss of 
pressure is nearly as the square root of the loss in pressure. 
From experiments made for friction in the long lines at the 
Mont Cenis tunnel it was found that the frictional loss in press- 
ure was 0.0936 — — , in which v was the velocity in feet per sec- 
ond, 1 the length of pipe in feet, and d the diameter of the pipe 
in inches. 

Other formulas were used in the experiments for obtaining 
the friction in long pipes in the Paris system, in which the 
velocity became a term in the equation, together with a coeffi- 
cient of decreasing value with the increase in size of the pipe. 

Thus the coefficient c was assigned to vary as .0027 ( 1 -|- ^ \ 

\ 10 d/ 

in which d is the diameter of the pipe in inches. 

Using D'Arcy's coefficients for the actual diameters of 
wrought-iron pipe, we have the discharge in cubic feet of com- 
pressed air per minute under the terminal pressure from a pipe 
of any diameter and length with various initial and terminal 



pressures from the following equation : D = c u " * P P* - 

w X length 



TRANSMISSION OF POWER BY COMPRESSED AIR. 



217 



in which d 5 is the fifth power of the actual diameter, p — p 2 , 
the difference between the initial and final pressures, w the 
density of the compressed air at the initial pressure as in col- 
umn 3, Table XXVI. ; the length of the pipe line in feet. 

In Table XXV. are given the nominal diameter of 
wrought-iron pipe of standard sizes, the actual diameter, the 
value of the coefficient c, and the value of the coefficient multi- 
plied by the square root of the fifth power of the actual diame- 
ter, c^/d 5 , which will facilitate computation. 

In Table XXVI., column 3, the weight of a cubic foot of 
compressed air is given for the pressures in column 1, multi- 
plied by the ratio in column 2, or by the formula, w = (.068 X 
P)-(-i X .0761, where P is the initial gauge pressure in pounds 
per square inch at the receiver or entrance to the transmission 
pipe. 

For any pressure not found in the tables the above formula 
may be used, as, for example, for 500 pounds gauge pressure 
.068 X 500 == 34 -f- 1 = 35 X .0761 = 2.663, the weight of 1 cubic 
foot of air at 500 pounds gauge pressure. This may also be 

obtained by the ratio of absolute compression X .0761. 5 4 '' 

14.7 
= 35 X .0761 = 2.663, as before. 

TABLE XXV.— Of Nominal and Actual Diameters and Areas of Stand- 
ard Wrought Iron Pipe. Coefficients and Multipliers for c^d 5 FOR 
Different-Sized Pipes. 



.St) 03 


"3 ° <A 


Is 


- m a 
Og 


1% 

> 


ago 


"3 £ « 


Is 


<i 6 

Gg 


ft 


I 


2 


3 


4 


5 


1 


2 


3 


4 


5 


2 

2>/ 2 

3 
3>A 

4 
4^ 


I.O48 

1.38 

1. 6l 

2.067 

2.46 

3.026 

3-56 

4.026 

4-5 



1 
2 
3 
4 
7 
9 
12 
15 


8626 

49 

03 

356 

73 

388 

83 

73 

93 


45-3 
' 47-3 
50.3 
52.7 
54-4 
56.1 
56.9 
57-8 
58.1 


45 

86 

138 

297 

537 

876 

1-304 

1,856 

2,492 


3 


3 


5 

6 

7 
8 

9 
10 
12 
14 
16 


5-025 
6.065 
7.023 
7.98 
8-937 
10.019 
12.00 
14.25 
16.4 


19.99 

28.888 
38.738 
50.04 
62.73 
78.839 
113.098 
I59-485 
211.24 


58.4 
59-5 
60.1 
60.7 
61.2 
61.8 
62.1 
62.3 
62.6 


3,298 
5,273 
7.817 
10,988 
14,872 
19,480 
30,926 
45,690 
64, 102 






218 



COMPRESSED AIR AND ITS APPLICATIONS. 



For the amount of free air corresponding with any given 
pressure multiply the gauge pressure by the ratio in column 2, 
Table XXVI. , or the volume of discharge for any terminal press- 



& b X P - P„ 



ure as found by the formula D = c 4/ 

r w X 1 

or by the ratio of compression as above explained. 



X column 2. 



TABLE XXVI. — Gauge Pressures and Corresponding Weight of a Cubic 
Foot of Compressed Air and its Square Root. 





Ratio 

of 

volumes. 


W 
weight of V v 
one cubic foot cc 




Gauge 


Ratio 

of 

volumes 




w 




Gauge 


weight, 
lumn 


weight of 
one cubic foot 


^/weight, 
column 






at pressure, 








at pressure, 






P 


column 1. 






P 


column 1. 




I 


2 


3 


4 


I 


2 


3 


4 


O 


I. OO 


0.0761 


276 


55 


4-74 


0.3607 


O.600 


5 


i-34 


. 1020 


319 


60 


5.08 




3866 


.622 


10 


1.68 


.1278 


358 


65 


5-42 




4125 


.642 


15 


2.02 


• 1537 


392 


70 


5.76 




4383 


.662 


20 


2.36 


.1796 


424 


75 


6.10 




4642 


.6Sl 


25 


2.70 


• 2055 


453 


80 


6.44 




4901 


.700 


30 


3- 04 


■ 2313 


481 


85 


6.78 




5160 


.718 


35 


3-38 


.2572 


507 


90 


7.12 




5418 


•736 


40 


3-72 


.2831 


532 


95 


7.46 




5677 


•753 


45 


4.06 


.3090 


556 


TOO 


7.80 




5936 


.770 


5o 


4.40 


.3348 


578 











As, for example, what amount of free air can be discharged 
through a 4-inch pipe 5,000 feet long; initial pressure 100 
pounds, terminal pressure 75 pounds? Then, as per above 
formula and per Table XXV., column 5, c V d" = 1,856, VP — P 2 
= V^S = 5 X 1,856 = 9,280, and from column 4, Table XXVI., 
Vw =.77 , V 5,000 feet = 70.71 ; then 70.71 X .77 = 54.44, and 



9,280 



170.4 cubic feet per minute at 75 pounds pressure. 



54-44 

The ratio in column 2, Table XXVI., is 6. 10 for 75 pounds and 

170.4 X 6.10 = 1,039.4 cubic feet of free air. 

The following tables of free air delivery for various initial 
pressures, and for differential pressure losses for lengths of 500 
feet for the actual diameter of pipes, were computed by Mr. 
William Cox for Mr. W. L. Saunders, and have been kindly 
loaned the author for this work. 



TRANSMISSION OF POWER BY COMPRESSED AIR. 219 

TABLES OF COMPRESSED-AIR TRANSMISSION. 

{Computed by William Cox.) 

With a Discharge of Equivalent Free Air in Cubic 
Feet per Minute from Pipes of Various Diameters 
from 1 to 10 Inches, Each 500 Feet Long, with 
Various Reductions of the Final Pressure. 

From these tables, approximate quantities and loss of press- 
ure may be obtained for any required length of pipe line. 

For Example. — It is required to deliver 2,000 cubic feet of 
equivalent free air at the end of a pipe line 150 feet long, the 
initial pressure being 60 pounds, and the loss of pressure not to 
exceed 10 pounds. What diameter of pipe must be used? 

TABLE XXVII. — Air Transmission. Initial Gauge Pressure, 45 Pounds. 







Reduction of Final Pressure in soo 


Feet. 




Diameter of 
















pipe. 


1 pound. 


2 pounds. 


3 pounds. 


5 pounds. 


7 pounds. 


9 pounds. 


12 pounds. 


i inch 


14 


20 


24 


30 


34 


37 


40 


1% inches. 


26 


36 


44 


54 


62 


68 


74 


i# " 


43 


60 


72 


90 


102 


112 


121 


2 " 


95 


132 


159 


198 


226 


247 


268 


*% " 


172 


239 


287 


358 


409 


446 


4S4 


•} " 


281 


390 


470 


585 


667 


728 


791 


3K " 


419 


583 


701 


874 


997 


1,080 


1,180 


4 


595 


827 


995 


1,240 


1,410 


1,540 


1,670 


4K " 


806 


1,120 


1.340 


1,680 


1,910 


2,090 


2,270 


5 


1,050 


1,470 


1,770 


2,200 


2, 510 


2,740 


2,980 


6 


1,690 


2,350 


2,820 


3.52o 


4,020 


4.380 


4,760 


7 


2,500 


3,48o 


4.190 


5,220 


5.950 


6,500 


7, 060 


8 


3.520 


4,900 


5.890 


7.340 


8,37o 


9.140 


9,930 


9 


4.770 


6,630 


7,97o 


9.930 


11,300 


12,300 


13,400 


10 " 


6,240 


8,680 


10,400 


13,0.0 


14,800 


16,100 


17,600 



By table of 60 pounds initial pressure under 3 pounds loss, 
and opposite 5-inch diameter of pipe, we see that the delivery 
would be 2,000 cubic feet, so that for a pipe line 1,500 feet long 

1 = 9 pounds. We 



the loss of pressure would be about 3 X 



500 



say " about " 9 pounds, because the loss is not exactly propor- 
tional to the length, but nearly so when the basis of length is 
500 feet. 



220 COMPRESSED AIR AND ITS APPLICATIONS. 

TABLE XXVIII. — Air Transmission. Initial Gauge Pressure, 60 Pounds. 







Reduction of Final Pkessure in 500 


Feet. 




















pipe. 


i pound. 


2 pounds. 


3 pounds. 


5 pounds. 


7 pounds. 


9 pounds. 


12 pounds. 


i inch 


16 


22 


27 


34 


39 


43 


48 


1% inches. 


29 


41 


49 


62 


72 


79 


37 


iK " 


43 


67 


81 


102 


117 


129 


143 


2 


107 


149 


180 


226 


259 


286 


315 


2"H " 


i93 


269 


325 


408 


469 


5i6 


569 


3 


3i5 


440 


532 


667 


716 


344 


930 


3/ 2 " . 


47i 


657 


794 


996 


1, 140 


1,260 


1,380 


4 


663 


932 


1, 120 


1,410 


1,620 


1,780 


1,970 


4^ " 


9°5 


1,260 


1, 520 


1,910 


2, 190 


2,420 


2,660 


5 


1,180 


1,650 


2,000 


2,510 


2,880 


3,i7o 


3-500 


6 


1,890 


2,650 


3,200 


4,010 


4,610 


5,o8o 


5.590 


7 


2,810 


3,920 


4,740 


5.95o 


6,840 


7.530 


8,290 


8 


3,960 


5,520 


6,670 


3,370 


9,620 


10, 500 


I I , 600 


9 


5,350 


7,470 


9,020 


11,300 


13,000 


14,300 


15,700 


IO 


7,010 


8,710 


11,800 


14,800 


17,000 


18,700 


20, 700 



TABLE XXIX. —Air Transmission. Initial Gauge Pressure, 75 Pounds. 







Reduction of Final Pressure in 500 


Feet. 




















pipe. 


1 pound. 


2 pounds. 


3 pounds. 


5 pounds. 


7 pounds. 


9 pounds. 


12 pounds. 


1 inch 


18 


25 


30 


38 


44 


43 


54 


\% inches. 


32 


45 


55 


69 


80 


89 


98 


1^ " 


53 


74 


90 


113 


131 


145 


161 


2 " 


117 


164 


199 


251 


289 


320 


356 


2^ " 


212 


296 


359 


453 


523 


579 


643 


3 


346 


484 


587 


740 


855 


946 


1,050 


3% " 


517 


723 


876 


1, 100 


1,270 


1,410 


1,560 


4 


734 


1,020 


1,240 


1,560 


I,8lO 


2,000 


2,220 


4/z " 


994 


1,390 


1,680 


2, 120 


2,450 


2,710 


3,010 


5 


1,300 


1,823 


2,210 


2,780 


3,220 


3,56o 


3,950 


6 


2,080 


2,9IO 


3.530 


4,450 


5,140 


5,690 


6,320 


7 


3,090 


4.320 


5.230 


6, 600 


7,630 


8,440 


9,370 


8 


4,350 


6,070 


7.360 


9,290 


10, 700 


11,800 


13,100 


9 


5,88o 


8,220 


9,963 


12,500 


14, 500 


16,000 


17,800 


10 " 


7,710 


10,700 


13,000 


16,400 


19,000 


21,000 


23,300 



Professor Unwin has estimated that 10,000 horse power can 
be transmitted at an initial pressure of 132 pounds a distance of 
20 miles in a 30-inch main with a loss of pressure of only 12 per 
cent ; and that the motor efficiency at this distance may vary 
with cold air from 40 to 50 per cent and by reheating - to 300 F. 
from 59 to 73 per cent. The air velocity for these estimates is 
based on 20 feet per second for best effect. The larger mains 
indicate a large saving in power for compression or for motor 
use, and indicate financial economy in the long run, especially 



TRANSMISSION OF POWER BY COMPRESSED AIR. 22 1 

where future possibilities may require additional air power. 
One of the great mistakes heretofore made in piping mining 
and other air systems has been due to a false estimate of future 
wants or a mistaken judgment of the loss in air friction. 

TABLE XXX. — Air Transmission. Initial Gauge Pressure, 90 Pounds. 







Reduction of Final Pressure in soo 


Feet. 




















pipe. 


1 pound. 


2 pounds. 


3 pounds. 


5 pounds. 


7 pounds. 


9 pounds. 


12 pounds. 


i inch 


19 


27 


33 


41 


48 


53 


60 


1^ inches. 


35 


49 


59 


75 


87 


97 


109 


i# " 


57 


80 


97 


123 


143 


159 


178 


2 " 


127 


178 


215 


273 


316 


35i 


394 


2/ 2 " 


229 


321 


390 


493 


572 


635 


712 


3 


375 


525 


636 


806 


934 


1,030 


1,160 


3% " 


560 


784 


95o 


1,200 


I.390 


i.55o 


1,730 


4 " 


794 


1,110 


1.340 


1,700 


1,980 


2,190 


2,460 


4J^ 


1,070 


i.5oo 


1,820 


2,310 


2,680 


2,970 


3.330 


5 


1,410 


1,970 


2,390 


3.030 


3,510 


3.900 


4.37o 


6 


2,250 


3,160 


3,830 


4.850 


5,620 


6,240 


6,990 


7 


3.340 


4,680 


5,68o 


7,190 


8,340 


9,260 


10,300 


8 


4,700 


6,593 


7.990 


10, 100 


11,700 


13,000 


14.500 


9 


6, 360 


8,930 


10,800 


13,600 


15,800 


17,600 


19, 700 


10 " 


8,340 


11,600 


14, 100 


17,900 


20, 700 


23,000 


25,800 



TABLE XXXI. — Air Transmission. Initial Gauge Pressure, 105 Pounds. 







Reduction of Final Pressure in 500 


Feet. 




















pipe. 


1 pound. 


2 pounds. 


3 pounds. 


5 pounds. 


7 pounds. 


9 pounds. 


12 pounds. 


i inch 


20 


29 


37 


44 


52 


58 


65 


1 % inches. 


37 


52 


68 


81 


94 


105 


118 


1^ " 


61 


86 


ill 


133 


155 


172 


194 


2 


129 


190 


245 


294 


34i 


380 


427 


2% " 


245 


344 


443 


531 


617 


687 


772 


3 


401 


562 


724 


867 


1,000 


1, 120 


1,260 


3^ " 


599 


839 


1,080 


1,290 


1,500 


1,670 


1,880 


4 


850 


1,190 


I.530 


1,830 


2,130 


2,370 


2,670 


4^ " 


1,150 


1. 610 


2,070 


2,480 


2,890 


3,220 


3,6lO 


5 


1,510 


2,110 


2,720 


3,260 


3.790 


4,220 


4.750 


6 


2,410 


3.38o 


■ 4.350 


5.220 


6,070 


6,760 


7,590 


7 


3,58o 


5,oio 


6,460 


7,740 


8,990 


10,000 


11,200 


8 


5,030 


7.050 


9,080 


10, 800 


12,600 


14,000 


15,800 


9 


6,810 


9.540 


12,200 


14, 700 


17,100 


19,000 


21,400 


10 " 


8,920 


12,500 


16,100 


19,200 


22,400 


24, 900 


28,000 



Air losses in transmission in pounds per square inch for defi- 
nite volumes through assigned pipe sizes, at the most-used 
pressure in mining and mechanical operations, viz., 80 pounds 
pressure, are given in Table XXXII. : 



22J 



COMPRESSED AIR AND ITS APPLICATIONS. 



TABLE XXXII. — Loss of Pressure through Friction of Air in Pipes, 
in Pounds per Square Inch for Every ioo Feet Length of Pipe 
(Initial Gauge Pressure 80 Pounds at Receiver). 



alent 
me 
e air 
arg-e 
nute. 












Size of Pipe. 


































,'i.S. P-z'p 
















































































H °^1 


1". 


!*'■ 


iH 


. 2". 


*% 


• 3 "- 


4". 


5"- 


6". 


7"- 


8". 10". 


12". 


14". 


25 


.24 


.12 


























50 


1. 00 


45 




3 






















75 


2 4 


1 


■4 
























IOO 




1-7 


7 
3 ° 


D .13 
5 50 


•17 


5 


















300 








I 20 


•3« 


•15 


















400 








2 '5 


.67 


.27 


.06 
















500 








3 3° 


1 10 


.40 


.10 


•°3 




012 












75° 










2 50 


.91 


.22 
.40 


.07 
.12 




°3 
°5 


013 
023 


012 








1,500 












400 


1 00 


•3° 




12 


052 


027 








2,000 














1.60 


■5° 




20 


°95 


048 


017 






3,000 














3 7° 


1.20 




45 


22 


"5 


036 


.015 




4,000 
















2 00 




80 


39 


20 


07 


.026 


.012 


5,000 


















1 


3° 


60 


3° 


10 


.041 


.018 


6,000 


















1 


9 


85 


43 


i.S 


.06 


.028 


7.5°° 


















3 


00 1 


40 


68 


22 


.09 


.04 


I0,000> 


















2 


5 1 


25 


40 


■17 


075 



Example. — An air compressor furnishes 500 cubic feet of 
free air per minute at a pressure of 80 pounds per square inch 
in the receiver. If this air is used at the end of a 3-inch pipe 
1,000 feet long, the loss due to friction will be 10X4 = 4 
pounds. If the same volume of air were supplied by the same 
compressor at the same pressure and passed through a 5-inch 
pipe, 1,000 feet long, the loss would be only .03 X 10 = 3 — 10 
pounds; thus illustrating the importance of using pipe of large 
diameter. Strictly speaking, the loss of pressure is not directly 
proportional to the length ; however, for all practical purposes 
it may be taken as such. 

The foregoing table represents the loss by friction in the 
pipe. There is a further slight loss due to the friction of the air 
with itself at the mouth of the pipe as it leaves the receiver. 

All leaks in compressors or valves, air receivers, or pipe, 
should be strictly guarded against for the sake of economy in 
the running of compressed air and steam apparatus. Air leaks 
are fully as expensive as steam leaks, and should be as care- 
fully stopped. Too many operators think that an air leak is of 
but little consequence, but it should never be allowed, save 
where needed for actual ventilation. 



Chapter XV. 



COMPRESSED-AIR 

REHEATING AND ITS 

WORK 



COMPRESSED-AIR REHEATING AND ITS WORK. 




One of the most important economies in the use of com- 
pressed air is the saving obtained by the increased volume due 
to reheating. The first efforts made in this line were probably 
suggested by the tendency of rock drills to become so frosted in 
the exhaust as to interfere with their best work. 

Experiments made by placing a wad of oily waste in a cham- 
bered fitting, close to the steam chest of a drill, which was 
found to burn freely fed by the 
passing air, led to trial of a miner's 
lamp in a small chamber, by which 
arrangement the products of com- 
bustion were added to the compressed 
air and, passing through the cylin- 
der, modified in a great measure the 
intensity of the frosty exhaust. 

In Fig. 6 1 this simple reheater is 
illustrated in its primitive form. The experiment clearly de- 
monstrated the possibility of utilizing the heat and products of 
combustion for their full value. 

Another experiment in the same line is shown in Fig. 62, 
in which any easily combustible fuel can be enclosed in a cham- 
ber above a wire-gauze partition in an enlarged fitting close to 
the air chest. An opening in the fitting, not shown in the cut, 
allows of igniting the combustible in contact with the wire 
gauze, when the combustion is kept up by the passing air and is 
fed by gravity from above. This method of reheating intensi- 
fies combustion and is fairly safe in mine drilling and pumping. 

Another form of internal combustion reheater, patented by 
"Edison," is illustrated in Fig. 63, and consists of a chamber 
'5 



Fig. 61.— simple reheater. 



226 



COMPRESSED AIR AND ITS APPLICATIONS. 




within a chamber, between which the air flows and is heated 
by a fire within the internal chamber. A by-pass regulated by 

a valve allows enough air to 
pass under the grate to feed 
the fire. A jacketed pipe 
leads the products of com- 
bustion from the top of the 
fire-chamber to the follow-, 
ing main air pipe, also regu- 
lated by a valve. A closure 
in the main intake air pipe 
produces a differential press- 
ure which insures circulation 
through the fire-chamber. 
A hand-hole plate at the 
top fastened by a yoke and 
screw allows of access for 
feeding fuel, and a full-sized 
head and yoke at the bot- 
tom allow of thorough cleaning. In ordinary operation the fire 
can be fed and ashes blown out without interrupting the main 
flow of air, by operating the by-pass valves. 

Reheaters of the class used in the Popp compressed-air sys- 
tem in Paris are made with pipe coils in a stove for small 
motors, and with cast-iron double-chambered stoves in which 
the products of combustion are carried to a chimney and wasted. 
The Sergeant reheater (Fig. 64) is a 
double-chambered stove in which all the 
compressed air passes vertically through 
the space between the fire-box and the 
outer shell. The fire is fed from the 
top, and can be stoked through the open 
grate at the bottom. 

This form of reheater is in general 
use, and is as simple and easily managed 



Fig. 62.— rock-drill reheater. 




COMPRESSED-AIR REHEATING AND ITS WORK. 22 7 

as is possible under most of the conditions available for econo- 
mizing the use of compressed air in motor engines. 

From tests made with this heater it has been found capable, 
of heating 340 cubic feet of free air per minute at 40 pounds 
pressure to 360 F., giving a gain of 35 per cent in the meas- 




-.-. 






Fig. 64. —the sergeant keheater. 



ured amount of work done by the air after passing through the 
heater, compared with the same volume of air when used cold. 
A heater of this size will heat less air to a higher tempera- 
ture or more air to a lower temperature, than stated above; 
but if it should be required to heat more than 400 cubic feet of 
free air per minute, to get the best economy it is advisable to 
use the heaters in series, allowing about 400 cubic feet of free 
air per minute for each heater. The heater should be placed 



228 COMPRESSED AIR AND ITS APPLICATIONS. 

as near as possible to the point where the air is to be used, and 
the outlet pipe should be as short as possible and well covered, 
so that the air will retain its heat. 

Trials have been made in reheating compressed air by in- 
jecting steam into the air pipe near the motor, by passing the 
air through a steam boiler, and in the Mekarski and other com- 
pressed-air systems by passing the air through a tank charged 
with water at a high temperature. 

Experiments have been made with a combination of steam 
with compressed air with an economy of 25 per cent in air vol- 
ume by an expenditure of 1 ^ pounds of coal per horse-power 




Fig. 65.— the "sergeant." 
Reheating the air for rock-drilling and pumping in Jerome Park Reservoir. 

hour for the steam used, and was found to be equivalent to an 
additional horse power for each pound of coal burnt in the 
heater. 

In consideration of the unavailability of steam except in a 
few locations where steam at high pressure is in use near the 
location of compressed-air engines, the heating of compressed 
air by steam for motors is of little or no practical value. Re- 
heating by the hot-water system as used on railway cars has 
proved very economical. 

The reheater of the Rand Drill Company, New York City, 
is illustrated in Figs. 66 and 67, and has a furnace lined with 
fire-brick and an ordinary fire and ash-pit door. The heating 
surfaces are composed of concentric annular spaces of gradually 



COMPRESSED-AIR REHEATING AND ITS WORK. 



229 



increasing area, keeping the velocity of the expanding air con- 
stant. The air enters at the side of an annular chamber shown 
in Fig. 67, passing around the heater and upward and down- 




FIG. 66.— THE RAND REHEATER. 



ward and then upward through the thin annular spaces, making 
its exit at the top of the interior and hottest space. 

In a test with a reheater of this type having % l / 2 square feet 
of heating surface, 530 cubic feet of free air under 60 pounds 
pressure were heated from 84 to 376 F. in one minute; with 
exhaust air from the motor, as a forced draft, the temperature 



230 



COMPRESSED AIR AND ITS APPLICATIONS. 



was raised to 450 F. for the same quantity of air; 300 is the 
most practicable temperature to operate motors and drills on 
account of oil lubrication ; but the air temperature at the re- 
heater may be higher to compensate for the distance of trans- 
mission. 

The use of superheated water forced into tanks for car motor 
service has become an established system, showing the best 




Fig. 67. 

economy for this class of service, and seems to be the only 
available means that does not require the management of a fire 
on the motor car. 

The hot-water reheater of the Mekarski system as used on 
a number of compressed railways in England, France, and 
Switzerland is illustrated in Fig. 68. The reheater is charged 
at the station with water at about 100 pounds or more pressure 



COMPRESSED-AIR REHEATING AND ITS WORK. 




Fig. 68.— mekarski ue- 

HEATER. 



at a temperature at or above 338 F., containing nearly 1,200 
heat units per pound of water. In the early water reheaters 
of this class the air was injected from a 
nozzle in the bottom of the heater as 
shown in the cut, and thereby absorb- 
ing water vapor to saturation with but 
little excess of steam. In Fig. 69 is 
illustrated the details of this reheater as 
used on the Nantes, France, compressed- 
air tramway, in which the compressed 
air enters the heater at the side near 
the bottom, and is divided into small 
streams issuing from a perforated pipe 
and, bubbling up through the water, be- 
comes heated to the temperature of the 

water, and also takes a considerable excess of hot vapor or 
steam, depending upon the relative pressures of the air and the 
pressure due to the temperature of the 
water. 

A diaphragm above the water line 
serves to prevent particles of water 
from escaping through the reducing 
valve when thrown up by the agita- 
tion of the passing air. The reduc- 
ing or regulating valve is of a peculiar 
construction as shown in the cut. The 
hand-wheel when turned lowers or 
raises a plunger; this acts upon a 
liquid contained between it and a 
diaphragm resting upon the head of 
a spring valve closing against the res- 
ervoir pressure. 

Just around the plunger there is an 

annular air space acting as an air ves- 

. - . * 1 ; sel. When the plunger is depressed 




232 COMPRESSED AIR AND ITS APPLICATIONS. 

into the liquid, the result is to compress the air in the air vessel 
to any desired extent. Then, on the air cock being opened, 
air bubbles through the hot water, and. rises past the cone valve, 
which is attached to the diaphragm into the space below it, so 
as to press on the under-side of the diaphragm and tend to raise 
it ; but it cannot do so until the pressure of the air below the dia- 
phragm equals that in the annular air vessel above, and thus 
the pressure in the annular air vessel is automatically the meas- 
ure of the pressure that will prevail in the engines. So soon as 
this is exceeded the diaphragm rises and closes the valve; and 
so soon as it falls the air in the annular air vessel re-expands 
and lets in more compressed air. In this way the driver can, 
from time to time, vary the pressure by his hand-wheel, confi- 
dent that, whether the engines are running quickly or slowly, 
the pressure will be steadily maintained. The automatic reg- 
ulating valve and the employment of the " hot-water chamber ' ; 
are the distinguishing features in this particular system — the 
Mekarski system — of using compressed air. 

The economic value of reheating compressed air in close 
proximity to an air motor or engine by a surface heater of the 
Sergeant, Rand, or Edison type is fully shown in column 2 of 
Table XV., which gives the increase in volume from any initial 
temperature to any other temperature at which the air emerges 
from the heater. 

In a surface heater of good form the loss of fuel heat from 
radiation and by the smoke-pipe should be no greater than 50 
per cent of the total heat value of the fuel, or, say for coal, a 
useful effect of 7,000 heat units per pound. This should heat 

Ll = 29,463 pounds of air i° F. If to be heated from 6o° 

to 360 , at which temperature the volume would be increased, 
as found in column 2, Table XV., from 13 cubic feet to 20.63 

cubic feet per pound; or — = 63 per cent by reheating to an 

20.63 

amount of 300 . Then 29 ' 4 3 = 94.8 pounds heated from 6o° 

300 



COMPRESSED-AIR REHEATING AND ITS WORK. 



33 



to 360 , and 94.8 x 13 = 1,232.4 cubic feet of initial free air, 
heated from 6o° to 360 by 1 pound of coal. The increase in 
volume equals 1,232 X .63 per cent, or yj6 cubic feet. Then 
if 10 cubic feet per minute represents 1 horse power in an air 
motor at any specified pressure, there should be a production 
of 77 horse power by reheating air to an amount of 300 by the 
burning of 1 pound of coal per minute, or 1.28 of a horse 
power per 1 pound of coal per hour, a far better result than can 
be anticipated from any known condition of steam power. 

When the entire products of combustion are utilized there 
is no loss save radiation, and we can safely count on 90 per 




Fig. 70.— automobile reheater. 

cent of the total heat units for effective work in reheating com- 
pressed air for power. Thus by the internal combustion sys- 
tem the saving of 2.4 horse power per pound of coal per hour 
may be accomplished. 

The method of reheating compressed air for automobile 
motors is shown in Fig. 70. The air stored at high pressure 
issues through a copper coil at reduced pressure controlled by 
link-valve gear, and reheated in its passage to the motor by 
gasoline or kerosene burners. 

Small storage-bottles of steel are made to hold 260 times 
their volume, or about 4,000 pounds pressure per square inch. 



234 COMPRESSED AIR AND ITS APPLICATIONS. 



THE CALORIC OR HOT-AIR ENGINE. 

The expansion and contraction of air by the absorption and 
elimination of its element of heat give to air a power for work 
which has been utilized to a small extent for motive power 
during the past century. The open-cycle system of its applica- 
tion in the early motor engines did not prove satisfactory or 
efficient. 

The most satisfactory and efficient system has been derived 
from Carnot's suggestion of the closed cycle of heat transfer in 
which the pressure element of air is kept within the motor, 
while the heat element is generated from the outside, trans- 
mitted through the enclosed air for work, and eliminated at 
the cold end of the cycle by a cooling medium; and then the 
air is returned to the heat-imparting chamber by the alternat- 
ing of two pistons. 

This is the type of the action of the Ericsson pumping en- 
gine with tandem pistons in a single cylinder, and the Rider 
two-cylinder hot-air engine. Other hot-air engines are of the 
Roper type in which the heat products of combustion from an 
internal furnace are absorbed in or mixed with the air in its 
open-cycle progress through the motor, the furnace being fed 
with air from a pump driven by the motor. The hot air and 
gases are exhausted from the cylinder at the close of each 
power stroke. 

Some trouble has been found in this class of hot-air motors 
from the ashes lodging in the working parts, and so clogging 
and wearing the surfaces. 

The rapid wear of working surfaces of valves and cylinder, 
and the difficulties in properly lubricating caused by the intense 
heat and ashes, have retarded their general use, apart from their 
bulky proportions. 

The Stirling hot-air engine, used in England and on the 
continent from 1816 and further improved about 1827, operated 



COMPRESSED-AIR REHEATING AND ITS WORK. 



235 



on the closed-cycle system with a regenerator, using the air at 
constant initial volume with pressures due to change of tem- 
perature and intensified by the capacity of the regenerator for 




ERICSSON PUMPING ENGINE WITH COAL-FIRE FURNACE. 



the absorption and elimination of heat from and to the air as it 
passed between the heating and cooling surfaces in the cycle. 
This engine required two cylinders, one of which was the 
power and cooling cylinder, and the other was the heating cyl- 



236 



COMPRESSED AIR AND ITS APPLICATIONS. 



inder containing the transfer piston. The modern Rider hot- 
air engine is an improved type of the Stirling engine. 

The Ericsson modern type of pumping engine, as made by 
the Rider-Ericsson Engine Company, New York City, has the 
power piston and transfer piston working tandem in the same 




FIG. 72.— SECTION OF ERICSSON pumping engine, with bunsen-burner gas furnace. 

1, Cylinder ; 2, air piston ; 3, transfer piston ; 4, heater ; 5, furnace ; 6, gas burners ; 7, air 
chamber ; 8, main beam ; 9, beam centre bearing ; 10, connecting rod ; 11, bell-crank link ; 12, 
bell crank ; 14, fly-wheel ; 15,. air piston links ; 16, pump link ; 17, pump chamber ; 18, pump 
gland ; 19, suction valve ; 21. suction pipe ; 22, pump bottom ; 25, crank-shaft bracket ; 26, 
crank ; 27, crank pin ; 29, transfer piston-rod, cross-head. 



cylinder, as represented in Figs. 71 and 72. It operates with- 
out a special regenerator. The hot air from the heating cham- 
ber passes in a thin stratum along the outside of the transfer 
piston, and is cooled in its course toward the working piston by 
convection from the water-jacketed surface of the upper part of 



COMPRESSED-AIR REHEATING AND ITS WORK. 237 

the cylinder, the pumped water passing through the cylinder 
jacket for this purpose. 

In the type of the Rider hot-air engine, operating through 
the same recurring cycle and at a constant initial volume with 
differential heat pressures, the extremes of heat and cold are 
established in different cylinders, the pistons being operated 
from a common shaft with cranks at right angles to meet the 
cyclic requirement, as shown in the cut (Fig. 73). The office of 
the regenerator is to intensify the extreme temperatures by 
absorbing much of the heat of the air as it passes from the heat 
cylinder to the cold cylinder, and to return the same heat to the 
air in its return from the cold to the hot cylinder. This opera- 
tion gives a greater range to the temperature, and thereby in- 
creases the range of pressures. 

Actual observation of the temperature at each end of the 
regenerator has shown a difference of 300 F., which indicates 
a considerable differential pressure, modified by the propor- 
tional part of the air volume in the two cylinders not acted 
upon by the regenerator. This may equal a mean differential 
temperature of 250 F. for the whole volume of the enclosed 
air. The respective volumes will then become as 1 to 1.27, 
and the pressures o to 4.23 pounds per square inch during a 
half revolution, with probably a mean pressure oi 2% pounds 
per square inch during a revolution of the fly-wheel. This will 
be equivalent to about 2,500 foot-pounds, minute, in a 5-inch 
engine, or nearly one-twelfth of a horse power. 

The indicator card (Fig. 74), taken from a Rider two-cylinder 
hot-air engine by Professor Hutton, represents the cycle of 
pressures derived from the apparently erratic motion of cranks 
at right angles and operated by two pistons, both of which were 
under variable pressure from heat expansion in a constant ini- 
tial volume of air. 

The drop of the indicator line below the atmospheric line 
during a half-stroke indicates a leakage of air under the press- 
ure of three half-strokes, or three-quarters of a revolution. 



2 3 8 



COMPRESSED AIR AND ITS APPLICATIONS. 




Fig. 73.— section of the rider hot-air pumping engine. 

A, Compression cylinder ; B, power cylinder ; C, compression piston ; D, power piston : 
E, cooler ; F, heater ; G, telescope ; 77, regenerator ; 77, cranks ; //, connecting rods ; K A', 
piston packings ; 7., check valve, at back of compression cylinder ; M, pump primer ; N, blow- 
off cock ; R, regenerator bonnet ; S S, pump-valve bonnet ; T, water jacket, to protect pack- 
ing from heat ; U U, pump buckets ; F, pump gland. 



COMPRESSED-AIR REHEATING AND ITS WORK. 239 

The hot-air engines of the Ericsson-Rider type do not oper- 
ate on the constant-volume cycle-, for the operation of the 
working pistons varies the relative volumes by the differential 
length of the cranks and consequent amount of the volume of 
the stroke, and also does not operate at constant pressure; 
hence, the heat volume of the air is variable. At constant 
pressure a motor piston cannot pass through a cyclical move- 
ment and do work. So that it becomes evident that in the in- 
vestigation of the movement of the pistons of this class of en- 
gines, the volume and pressure are both variable, and that 




Fig. 74.— indicator card. 
Rider hot-air engine. 

both volume and pressure are made variable by heat exchange 
and thus become the elements of motive power. 

In the traverse of the two pistons in the Ericsson type 
the transfer piston is neutral in pressure, save the air friction ; 
but in the Rider type the two pistons are of equal size, single 
acting, both working against the outer atmospheric pressure, 
and have the internal pressure equal on both pistons, save the 
air friction by transfer. Its power is derived from the differ- 
ential stroke, the transfer piston having the longest stroke by 
about 16 per cent. The Ericsson hot-air pumping engine is 
made in four sizes, viz., 5-, 6- 8-, and 10-inch diameter of cyl- 
inder. The Rider hot-air pumping engine is made in five 
sizes, viz., 4-, 5-, 6-, 8-, and 10-inch diameter of cylinders. 



Chapter XVI. 



THE COMPRESSED-AIR 
MOTOR 



THE COMPRESSED-AIR MOTOR. 

The published literature of recent date on the operation 
and efficiencies of compressed-air motors and the larger en- 
gines is too scant to quote their actual work at the present 
time; and especially when the engines of the present day are 
designed along the lines of the highest duty that can be given 
to the high-speed type and Corliss model. The operation of the 
latter is most desirable for obtaining the high efficiency that 
should be expected from the best designs and appliances for 
generating compressed air, and for its most useful work in our 
best-constructed engines with reheating appliances. 

Our principal source of information in regard to the oper- 
ation of compressed-air motors or engines is derived from the 
work of Professor Kennedy and others in their examinations 
and experiments at the compressed-air plant in Paris, France. 
From the class of compressors and motors in use at that time 
(1889) the results are not satisfactory; but it is hoped that the 
improvements in the efficiency of compressors and motors of 
the present day will enable us to show a considerable increase 
in the economy of the use of compressed air in compression, 
transmission, and for motive power, over these conditions as 
observed in the Paris plant. The small rotary engines in use 
in the Paris plant are convenient and compact, of high speed, 
and use the air with little or no expansion and without reheat- 
ing, and of course have no pretence to economy in the use of 
air. The larger-sized motors and engines of the reciprocating 
type are of the ordinary slide-valve gear with automatic cut-off, 
controlled by a governor, and mostly provided with reheaters, 
which have been gradually improved until the later models 
seem to be very efficient in raising the temperature of the ex- 
haust above the freezing-point. 



244 



COMPRESSED AIR AND ITS APPLICATIONS. 



Where refrigeration or cooling effect from the exhaust is 
desired, the reheater is modified or dispensed with. The value 
of reheating in the later forms of the Paris apparatus is to raise 
the temperature from 175 to 31 8° F. above the normal tempera- 
ture, or to increase the volume of compressed air up to 60 per 
cent greater than its normal volume, at a cost of two-tenths of a 
pound of coal per horse-power hour. (See article on reheating.) 

In Fig. 75 is a diagram or indicator card showing the con- 
ditions of air compression and motor work of this Paris plant 
as given by Professor Kennedy. It may be noticed in the dia- 




FlG. 75.— COMPRESSOR AND MOTOR WORK. 

gram that the compression was almost adiabatic as shown on 
the double line B C, showing want of jacket cooling, the upper 
line B C being adiabatic; the closeness of these lines being 
attributed partly to resistance in the discharge valves, so that 
the work of the compressors was practically adiabatic. The 
area A B C D E represents on any scale the work done in the 
steam cylinder, and the area A B C F the work done by the 
same scale on the air in the compressors. C G is the isother- 
mal line of compression, so that A G represents the volume of 
the compressed air when it has fallen in the mains to the ini- 
tial temperature at C. G H is the adiabatic curve of expansion 
from the volume at G; the area A G H F is 61 per cent of the 
area A B C F (and 52 per cent of the area A B C D E). It rep- 




THE COMPRESSED-AIR MOTOR. 245 

resents the maximum work that can be obtained in a motor 
without reheating. Again, if the pressure falls from A to K by- 
transmission, the volume increases from A G to K L, the point 
L lying on the isothermal line G C. The loss of possible work 
due to such a reduction of pressure is represented by the differ- 
ences between the areas A G H F and K L M F, in both of which 
the expansion curves are adiabatic. The area K N O P repre- 
sents the actual work of the motor without reheating, and the 
area K Q R P represents the actual 
work of the motor by reheating 
the air to 320 F. 

In Fig. j6 is shown a sample 
card from a 10 horse-power Eng- 
lish engine which was the subject 

/.,.'., f T-, ■ t ^ FIG. 76.— SLIDE VALVE CARD. 

of test m the Paris plant, and 

which represents the area K N O P in the diagram (Fig. 
75), and with 9.9 indicated horse power was using 14.8 cubic 
feet of free air per horse power per minute. The dotted lines 
are isothermal, and the contour of the card shows defects in the 
valves or their motion and irregular adjustment of cut-off. 

The theoretical power of the air used should have been 1 1.6 
cubic feet of free air per horse-power minute, making the indi- 
cated efficiency of the motor .79; but from undue weight and 
friction of the motor the mechanical efficiency was but .67. 

Late experiments with the rotary motors used in the Paris 
compressed-air system show a most extravagant use of free air 
per horse power, viz., 17.4 cubic feet per horse-power minute 
with cold air, and 13.9 cubic feet when the air was heated to 
122 F., with an efficiency of 43 per cent. 

Many of the motors now in use in Paris have an efficiency 
of only from 65 to 75 per cent, while a few of the best modern 
construction show a mechanical efficiency of 91 per cent. In 
one of the tests of late date, on an 80 horse-power engine that 
had been used as a steam engine, and for the purpose was sup- 
plied with an air reheater in which the temperature of the air 



246 COMPRESSED AIR AND ITS APPLICATIONS. 

used was 320 F., the engine used but 7.54 cubic feet of free 
air per horse-power minute, correspcnding to a total efficiency 
of 80 per cent. In this test the consumption of coke for re- 
heating was o. 176 pounds per horse-power hour. The exhaust 
air temperature varied somewhat in difference with various 
initial temperatures not readily accounted for. When the ini- 
tial temperature was 305 ° F. the exhaust was 84 , a difference 
of 221 . With 320 the exhaust was 95 , difference 225 , and 
with 338 the exhaust was 120 , difference 21 8°. 

For comparison with present and future work of compres- 
sion, transmission, and work of the motor, we give the follow- 
ing summary of the efficiencies of the Paris compressed-air 
plant as reported by Professor Kennedy, from which there has 
been but slight change, except perhaps in the later introduc- 
tion of more economical motors and an increase in the reheat- 
ing temperature : 

One indicated horse power at central station gives 0.845 in- 
dicated horse power in compressors, and corresponds to the 
compression of 348 cubic feet of air per hour from atmospheric 
pressure to 6 atmospheres absolute. 

Efficiency of main engines, 0.845. 

0.845 indicated horse power in compressors delivers as 
much air as will do 0.52 indicated horse power in adiabatic ex- 
pansion after it has fallen in temperature to the normal tem- 
perature of the mains. 

O K? 

Efficiency of compressors ' D ~ = 0.61. 
F 0.845 

The fall of pressure in mains between central station and 

Paris (say 5 kilometers) reduces the possibility of work from 

0.52 to 0.51 indicated horse power. 

Efficiency of transmission through mains '•> = 0.98. 

The further fall of pressure through the reducing valve to 
4}4 atmospheres (5^ atmospheres absolute) reduces the possi- 
bility of work from 0.51 to 0.50. 

Efficiency of reducing valve ~^— = 0.98. 

0.51 



THE COMPRESSED-AIR MOTOR. 247 

The combined efficiency of the mains and reducing valve, 
between 5 and 4V2 atmospheres, is thus 0.98 X 0.98 = 0.96. 
If the reduction had been to 4, 314, or 3 atmospheres, the cor- 
responding efficiencies would have been 0.93, 0.89, and 0.85 
respectively. 

Incomplete expansion, wire-drawing, and other such causes 

reduce the actual indicated horse power of the motor from 0.50 

to 0.39. 

Indicated efficiency of motor —^ = 0.78. 

0.50 

Indicated efficiency of whole process with cold air, 0.39. 

By heating the air before it enters the motor to about 320 
F., the actual indicated horse power at the motor is increased, 
however, to 0.54. The ratio of gain by heating the air is, 

therefore, 2l£^" = 1.38. 

°-39 
Apparent indicated efficiency of whole process with heated air, 
0.54. 

In this process additional heat is supplied by the combus- 
tion of about 0.39 pound coke per indicated horse power per 
hour, and if this be taken into account the real indicated effi- 
ciency of the whole process becomes 0.47 instead of 0.54. 
Real indicated efficiency of whole process with heated air, 0.47. 

Working with cold air the work spent in driving the motor 
itself reduces the available horse power from 0.39 to 0.26. 

Mechanical efficiency of motor, cold, 0.67. 

Working with heated air the work spent in driving the 
motor itself reduces the available horse power from 0.54 to 0.44. 
Mechanical efficiency of motor, hot, 0.81. 

Since the first instalment of the Paris plant a marked im- 
provement has been made in the design of the compressors of 
a new plant, in which two-stage compression and intercooling 
has been introduced, in which an efficiency of 98 per cent is 
claimed as between the indicated power of the engine and 
compressor. 



248 COMPRESSED AIR AND ITS APPLICATIONS. 

A HYDRAULIC AIR-COMPRESSING PLANT. 

The following abstract of a report furnishes some interest- 
ing details of the air plant of the North Star Mining Company, 
Grass Valley, Cal., and what has been and can be done through 
the medium of impact wheels under high water pressure: 

" For this plant the water supply is obtained from the South 
Yuba Water Company at a point on their canal about four miles 
from Grass Valley, Nevada County, Cal. Thence it is con- 
veyed about two and one-half miles to the Empire Mining 
Company's works in a 22-inch riveted iron pipe, built more 
than ten years ago. The new conduit is a riveted steel pipe, 
20 inches in diameter, joined to the lower end of this old one 
under a head of 420 feet, and continues 7,070 feet to the power- 
house, situated at the lowest convenient point on Wolf Creek, 
just below the town of Grass Valley, where a head of 775 feet, 
or a static pressure of 335 pounds per square inch, is obtained. 
The capacity of this pipe is sufficient to develop 800 to 1,000 
horse pow 7 er. 

"At the power-house there is a Pelton water-wheel, 18 
feet 6 inches in diameter, running on a 10-inch shaft, to which 
a duplex compound air compressor is connected directly. The 
initial cylinders are 18 inches, and the second cylinders are 10 
inches in diameter with a 24-inch stroke. They were designed 
to run at 110 revolutions per minute, and require 283 horse 
power from the water-wheel. 

" A 6-inch lap-welded pipe conveys the air at 90 pounds 
pressure from the power-house to the company's Stockbridge 
shaft on Massachusetts Hill, 800 feet distant and 125 feet 
higher. Here it is being used in a 100 horse-power cross- 
compound Corliss pneumatic hoisting engine, and a 75 horse- 
power compound pump, beside other pumps, blacksmith forge, 
drills, etc. 

" About 1,000 feet from the lower end a 12-inch branch with 
a gate is put in for possible future use, and near it is a 20-inch 



THE COMPRESSED-AIR MOTOR. 249 

gate. At the lower end of the pipe in the power-house there 
is another 20-inch gate, below which is a 12 -inch branch lead- 
ing to the Pelton wheel, and adjoining this is the receiver, 2 
feet in diameter, on which are the air chambers, charging tube, 
and relief valve. The air chamber is a 10-inch lap-welded tube 
18 feet long standing on the receiver, with an 8-inch gate be- 
tween. The charging tube is similar, but 8 inches in diameter. 
Both have 2 -inch water discharge pipes and gates, and by 
proper manipulation of the gates and the operation of inlet 
check valves on top of the tubes, the air chamber may be filled. 
Ordinarily the charging-tube is filled up to 90 pounds pressure 
from the air compressor delivery pipe, and then raised by the 
water pressure. It is found necessary to put in about one-tenth 
of the volume of the air chamber every day. Where the air 
goes is, thus far, a mystery, as no leak has been discovered." 
This should be no mystery, for it is well known that water 
under great pressure absorbs a large addition to its natural 
holding under atmospheric pressure. " The demand for direct 
action under a head of 775 feet made a large wheel necessary in 
order to obtain the proper peripheral speed of half the spouting 
velocity. This could not readily be done, and a wheel of iS}4 
feet diameter was made by the Pelton Company of San Francisco, 
who guaranteed an efficiency of 85 per cent of the water value 
at full load, and an average of 75 per cent from half to full load 
of the theoretical power of the water, and, at the same time, to 
so govern the wheel that it should not exceed 120 revolutions 
nor raise the air pressure above 105 pounds per square inch in 
case of accident to machinery or sudden shutting-off of air. 
The rim is built up of angles and plates riveted together to 
break joints. It weighs about 6,800 pounds, and is held con- 
centric with the shaft by twelve pairs of radial spokes of 1 y^ - 
inch rod iron held by nuts to the cast-iron hub. The driving 
force, being applied to the rim, is transferred to the hub by 
four pairs of 2 -inch iron rods, so arranged as to form a truss. 
The wheel is set on a 10-inch shaft, having a disc crank on 



250 COMPRESSED AIR AND ITS APPLICATIONS. 

either end and connected directly to the compressors. The 
regulator is a floating valve actuated against excessive velocity 
by the ordinary ball governor and against excessive air press- 
ure by a spring set to move when the air pressure in the de- 
livery pipe exceeds 90 pounds. 

" Repeated tests which checked very closely give the wheel 
an efficiency of a trifle over 90 per cent for one-quarter, one- 
half, three-quarters, and full loads. Between these points it is 
somewhat less, as the hood coming down over the nozzle tends 
to deflect the water as well as hold it back, and decreases the 
efficiency. It seems probable that the long radius of the 
wheel accounts for the high efficiency. 

" The compressors were built by the Fulton Engineering 
and Ship-Building Company of San Francisco. They are made 
very heavy, to stand the high piston speed required by the con- 
ditions of the water power. The compressor cylinders are 18 
and 10 inches in diameter and 24 inches stroke. 

" The most novel feature of these machines is the inter- 
cooler. This is made up of forty-nine soft copper pipes, 1 inch 
in diameter, 18 feet long, each with a stuffing-box at each end 
connected with manifold castings. The air delivered from the 
first cylinder into one manifold passes through these pipes to 
the other manifold, from which it is taken to the second cylin- 
der. The whole is placed in the wheel pit directly under and 
in front of the wheel, so that the water dashes all over and 
through it. The air, leaving the first cylinder at a temperature 
of 200 F., passes through the intercooler and enters the second 
cylinder at 6o°, slightly cooler than when entering the first cyl- 
inder. The temperature is again raised, to 204 on leaving the 
second cylinder and passing into the transmission pipe, show- 
ing a total rise in temperature of 282 F. from both stages. 

"The transmission pipe, conducting the air at 90 to 100 
pounds pressure about 800 feet from the compressors to works 
at the mine, is ordinarily well tubing 5^ inches in diameter 
inside. At the mine there is the ordinary air receiver and 



THE COMPRESSED-AIR MOTOR. 25 I 

also three 50-horse-power boilers set ready for steam, which are 
used for receivers. 

" The air is taken from these into the reheaters. It requires 
a little over half a cord of good pine wood each twenty-four 
hours to heat about 700 cubic feet of free air per minute to a 
temperature 350 to 400 F. The heated air passes through 
pipes covered with magnesia and hair-felt to the first cylinder 
of the hoisting engine, from which it is exhausted back into 
the upper heater, where its temperature is again brought to 
350 , whence it passes to the second cylinder at 30 pounds press- 
ure. From this it is exhausted through a flue to the change 
house, where it is used for heating and drying clothes. From 
the first heater also the air for the pump is conveyed some 300 
feet down the shaft in a similarly covered pipe. It receives 
the air at about 275 and exhausts it into the shaft at about 6o°, 
thus giving plenty of pure cool air to the men, without the 
usual fans or ventilators. 

" A direct-acting donkey pump is situated in another shaft 
750 feet distant, to which air is carried cold in a 2-inch pipe 
over the surface. An old hot-water heater is used as a reheater 
for the air, and consumes twelve sticks of pine cord-wood per 
twenty-four hours. 

" The hoisting engine is a compound direct-acting Corliss of 
100 horse power with cylinders jacketed for hot air, and is cal- 
culated to work 3,000 feet down an incline of about 35 . 

" There is 304 theoretical horse power in the water used at 
the power-house, the w-ork aactually accomplished at the mine 
amounts to 203 horse power, and the cost of reheating is $3 
per day. 

" Efficiency of compression and transmission from water 

wheel to motors, and not including cost of reheating 5 '^ = 79.5 per cent. 

■ 283 
Efficiency of compression and transmission from theoret- 
ical power of the water to the motors, and not in- 
cluding cost of reheating 5 " 3 = 74 per cent. 

304 
Efficiency from the water-wheel to and through the 

motors, not including reheating 202^7 _ ?J b per cent> 

283 



252 COMPRESSED AIR AND ITS APPLICATIONS. 

Efficiency from the theoretical power of the water, to 
and through the motors, and not including the cost 

of reheating — _ = 66 per cent. 

304 
Efficiency of compression and transmission from water- 
wheel to motors, including the cost of reheating ex- 
pressed in water power — ^A_ = 73 per cent. 

307.66 
Efficiency of compression and transmission from the the- 
oretical power of the water to the motors, including 

the cost of reheating expressed in water power ~ 5 ' 3 = 68.4 per cent. 

329 
Efficiency of compression and transmission from the 

water-wheel to and through motors, including cost 

of reheating expressed in water power ^'' = 65. 5 per cent. 

307.66 
Efficiency of compression and transmission from the the- 
oretical power of water to and through the motors, ' 
including cost of reheating expressed in water power. — — - = 61.6 per cent. 

Horse power of air at works after reheating 225.32 

Horse power delivered to compressors by water-wheel 283 

Theoretical horse power of water used on the wheel 304 

Horse power of work actually done by the motors 202. 7 

The horse power delivered by the water-wheel to the 

compressor, to which is added the horse power (24.66) 

which the cost of the wood used in reheating would 

buy in water 307.66 = 283 -|- 24.66 

The theoretical horse power of the water used on wheel 

added to the horse power (24.66) which the cost of the 

wood used in reheating would buy in water 329 = 304 -j- 24.66 " 

It may be urged that the conditions are particularly favor- 
able to compressed air, as the transmission is short and the 
power is not needed for tramways or lighting. But were it 20 
miles instead of 1,000 feet, it is thought by the author that, 
taking the whole plant, compressor, transmission pipe, and 
motor, as against generator, transmission wires, transformers, 
and electric motors, the air will prove cheaper in first cost, 
higher in efficiency, less liable to accident, and less expensive 
to operate and maintain than by electric transmission and 
power. 

The hydraulic power air plant of the hydraulic power com- 
pany at Iron Mountain, Mich., is said to be the largest com- 
pressed-air plant in the United States. It utilizes the water- 
power of the Quinnesec Falls, which are 47 feet high. A 
separate turbine operates three duplex compressors 32 x 60 
inches and one duplex compressor 36 x 60 inches, with a capac- 



THE COMPRESSED-AIR MOTOR. 



253 



ity of about 16,000 cubic feet of free air per minute compressed 
variably from 62 to 67 pounds pressure per square inch. The 
compressed air is transmitted 3 miles through a 24-inch conduit, 
with loss in pressure of from 2 to 3 pounds per square inch, 
and then distributed through 1,500 feet of variable-sized pipes 
to hoisting engines, air pumps, rock drills, and engines for run- 
ning dynamos for electric lighting. 

In Fig. 77 is a reduced copy of an indicator card from an 
automatic Corliss engine, 10 x 30 inches, 86 revolutions, and 65 
pounds pressure in the air pipe ; air at normal temperature of 




Fig 77 —Corliss engine air card. 

70 F. ; cut-off .175, which with 4 per cent clearance makes the 
real cut-off, as per Table XXII., .206, for which the theoretical 
mean pressure should be, for the air entrance pressure of 59 
pounds, 73.7 X .4369 = 32.19 — 14.7 = 17.49 pounds, the mean 
pressure. By the indicator card the measured mean pressure 
of the head end is found to be 19.21. The dotted line's on the 
card show the theoretical adiabatic curve, the terminal press- 
ure of which is shown by the formula, 73.7 X.1041 = 7.67 — 
14.7 = — 6.03. The final temperature of the exhaust should 
have been by the ratio for volumes from 70 F. expanded from 
.206 real cut-off .5192 X 530 = 275 — 460 = — 185 F. 

The ratios may be taken from Tables XVI. and XVII. for 
small divisional parts by interpolation ; or the terminal temper- 



ature may be obtained from the equation 



R 



R the ratio 



254 



COMPRESSED AIR AND ITS APPLICATIONS. 



is = 4.854 log. 0.6861 X .408 = 0.27992, index of which 

.206 



is 1.905 and 



1.905 



5248 X 530 = 278 — 460° 



i82°F. 



The indicator card (Fig. 78) is from the same engines as 
above, with a pressure of 58 pounds in the air pipe, valve partly 
throttled so that the entrance pressure was but 48 pounds, and 
the cut-off automatically extended to .22 and the real cut-off by 
the clearance .25. The air was taken through a reheater and 




-ISfaba'tic Line ^SSStSTSSi 

Fig. 78.— Corliss engine air card. 

entered the cylinder at a temperature of 310 , making the mean 
pressure by measurement but slightly less than the previous 
card, and exhausting below the atmospheric pressure about im- 
pounds and 6 pounds above the adiabatic theoretical line as 
shown by the dotted line. The final temperature as found 
from the ratio of expansion, which is 4 log. 0.60206 X-4o8 = 



0.24564, index 1.761, and 

-23°. ' 



1. 76 1 



5678 x 77o = 437 - 460 






Chapter XVII. 



EFFICIENCY OF AIR 

COMPRESSORS AT HIGH 

ALTITUDES 



EFFICIENCY OF AIR COMPRESSORS AT HIGH 
ALTITUDES. 

As the density of the atmosphere decreases with the alti- 
tude, a compressor located at a high altitude takes' in less air at 
each revolution, that is to say, the air is taken in at a lower 
pressure ; hence the early part of each stroke is occupied in 
compressing the air from the lower density up to the normal 
sea level pressure of 14.7 pounds, and the volumetric capacity 
of the air cylinder is correspondingly diminished. The power 
required to drive the same compressor is also less than at sea 
level, but the decrease in power required is not in as great a 
ratio as the reduction in capacity. Therefore, compressors to 
be used at high altitudes should have the steam and air cylin- 
ders properly proportioned to meet the varying conditions at 
different altitudes. The compressor friction and leakage losses 
are a constant quantity. 

It is apparent that the denser the air is when drawn into the 
compressor cylinder, the sooner the desired pressure is reached 
in terms of the cylinder stroke, and, on the contrary, the lighter 
or less dense the air is at the intake, the smaller will be the 
volume at the desired pressure, or the pressure is reached at a 
later point in the stroke. The volumetric efficiency of an air 
compressor will therefore be inversely as the mean pressure, 
and the loss of capacity will be the complement of the efficiency. 

The air temperature at high levels is on the average lower 
than at. sea level throughout the year, which slightly increases 
the density due to the height alone ; so that the volumetric 
efficiency may be somewhat higher than is due to barometric 
pressure alone. 

The decreased power required by a compressor due to ele- 
vation varies from 60 to 56 per cent of the loss of capacity. 



258 



COMPRESSED AIR AND ITS APPLICATIONS. 



The following table shows the efficiency and loss in capacity 
of compressors working at different altitudes, also the approxi- 
mate decrease in power required as compared with the same 
compressor working at sea level, and delivering air at 70 pounds 
pressure per square inch : 

TABLE XXXIII. — Compressor Efficiencies at Different Altitudes. 





Barometric Pressure. 


Volumetric 

efficiency of 

compressor, 

per cent. 


Loss 

of capacity, 

per cent. 


Decreased 


Altitude, feet. 


Inches, 
mercury. 


Pounds per 
square inch. 


required, 
per cent. 




30.00 
28.88 
27.80 
26.76 
25.76 
24.79 
23.86 
22.97 
22.11 
21.29 
2O.49 
19.72 
18.98 
18.27 

17-59 
16.93 


14-75 
14.20 
I3-67 
13-16 
12.67 
12.20 
"•73 
11.30 
10.87 
10.46 
10.07 
9.70 
9-34 
8.98 
8.65 
8.32 


IOO 

97 
93 
90 

87 
84 
81 
73 
76 
73 
70 
68 
65 
63 
60 
53 


O 
3 
7 
10 
13 
16 

19 
22 
24 
27 
30 
32 
35 
37 
40 
42 






1.8 




3-5 

5-2 

6.9 

8-5 

TO. I 








6, 000 




11. 6 




13- 1 
14.6 
16. 1 








17.6 
19.1 
20.6 
22.1 

23-5 




13,000 

14,000 

15,000 



For pressures above 70 pounds as given in above table, de- 
duct 3 per cent from the tabulated figures in column 4 and 10 
per cent in column 6 for each 10 pounds approximate. 



CAPACITY OF AIR COMPRESSORS. 

To ascertain the capacity of an air compressor in cubic feet 
of free air per minute, the common practice is to multiply the 
area of the intake cylinder by the feet of piston travel per min- 
ute. The free air capacity of the compressor divided by the 
number of atmospheres will give the volume of compressed air 
per minute. To ascertain the number of atmospheres at any- 
given pressure, add 1 5 pounds to the gauge pressure, divide 
this sum by 15, and the result will be the number of atmos- 
pheres. 

The above method of calculation, however, is only theoret- 
ical, and these results are never obtained in actual practice even 



EFFICIENCY OF AIR COMPRESSORS AT HIGH ALTITUDES. 



259 



with compressors of the very best design. Allowances should 
be made for losses of various kinds, the principal loss being 
due to clearance spaces ; but in machines of poor design and 
construction other considerable losses occur through imperfect 
cooling, leakages past the piston and through the discharge 
valves, and insufficient area and improper working of inlet 
valves. We have seen compressors in which the total air loss 
was from 10 to 20 per cent, whereas 3 to 10 per cent should be 
the maximum — according to size — in compressors of best de- 
sign and construction. 

The following table will be found useful for ascertaining 
quickly the capacity of an air compressor, also to find the 
cubical contents of any cylinder or receiver. 

The first column is the diameter of the cylinder in inches, 
the second shows the cubical contents, in feet, for each foot 
in length. To find the capacity of an air cylinder, multiply the 
figure in the second column by the piston travel in feet per 
minute ; this applies to double-acting air cylinders ; in the case 
of single-acting air cylinders the result should be divided by 2. 



TABLE XXXIV. 



-Contents of Cylinder in Cubic Feet for Each Foot in 
Length. 



Diam. 


Cubic 


Diam. ( 


^ubic 


Diam. 


Cubic 


Diam. 


Cubic 


Diam. 


Cubic 


inches. 


contents. 


inches, co 


ntents. 


inches. 


contents. 


inches. 


contents 


inches. 


contents. 


I 


• 0055 


5A 


1803 


io# 


.6013 


i8# 


I.867 


31 


5-241 


I* 


.0085 


6 


1963 


IO# 


.6303 


19 


I.969 


32 


5-585 


1% 


.0123 


6/ 


2130 


II 


.6600 


I9K 


2.074 


33 


5- 940 


1% 


.0168 


ty 2 


2305 


hX 


.6903 


20 


2.182 


34 


6.305 


2 


.0218 


6/ 


2485 


II# 


.7213 


20^ 


2.292 


35 


6.681 


2X 


.0276 


7 


2673 


113/ 


•7530 


21 


2.405 


36 


7.069 


2/ 2 


• 0341 


VA 


2868 


12 


•7854 


21K 


2.521 


37 


7.468 


2/ 


•0413 


1A 


3068 


™A 


.8523 


22 


2.640 


38 


7.886 




.0491 


VA 


3275 


13 


.9218 


22K 


2.761 


39 


8.296 


3 l A 


.0576 


8 


3490 


i3# 


.9940 


23 


2.885 


40 


8.728 


y/z 


.0668 


8X 


3713 


14 


I.069 


23^ 


3.012 


41 


9.168 


3 A 


.0767 


%A 


3940 


I4# 


1. 147 


24 


3-142 


42 


9.620 


4 


.0873 


*A 


4175 


15 


I.227 


25 


3.409 


43 


10.084 


*A 


.0985 


9 


4418 


I5# 


1. 310 


26 


3.687 


44 


10.560 


4/z 


.1105 


9% 


4668 


16 


I.396 


27 


■ 3-976 


45 


11.044 


4# 


.1231 


9A 


4923 


16^ 


I.485 


28 


4.276 


46 


11.540 


5 


.1364 


9A 


5IS5 


17 


I.576 


29 


4-537 


47 


12.048 


$A 


• 1503 


10 


5455 


I7# 


I.670 


30 


4.909 


48 


12.566 


S% 


.1650 


10X 


5730 


18 


I.767 











26o 



COMPRESSED AIR AND ITS APPLICATIONS. 



COMPRESSED AIR FOR HOISTING ENGINES. 

The following table is intended to give an approximate idea 
of the volume of free air required for operating hoisting en- 
gines, the air being delivered to the engines at 60 pounds 
gauge pressure. There are so many variable conditions to the 
operation of hoisting by the hoisting engines in common use 
that accurate computations can only be offered when fixed data 
are given. In the table, the hoisting engine is assumed to 
actually run but one-half of the time for hoisting, while the 
compressor, of course, runs continuously. If the engine run 
less than one-half the time, as it usually does, the volume of 
air required will be proportionately less, and vice versa. The 
table is computed for maximum loads, which also in practice 
may vary widely. From the intermittent character of the work 
of a hoisting engine the parts are able to resume their normal 
temperature between the hoists, and there is little probability 
of the annoyance of freezing up the exhaust passages. 



TABLE XXXV. — Volume of Free Air Required per Minute for Operating 

Hoisting Engines, the Air Compressed to 60 Pounds Gauge Pressure. 

Single Cylinder- Hoisting Engine. 



Diameter 

of cylinder, 

inches. 


Stroke, 
inches. 


Revo- 
lutions 

per 
minute. 


Normal 
horse- 
power. 


Actual 
horse- 
power. 


Weight 

lifted, 

single rope. 


Cubic 
feet of free 

required. 


5 


6 
8 
8 
10 
10 
12 
12 


200 
160 
360 
125 
125 
no 
no 


3 
4 
6 
10 
15 
20 
25 


5-9 
6-3 
9.9 
12. 1 
16.8 
1S.9 
26.2 


600 
1,000 
1, 500 
2,000 
3,000 
5,000 
6,000 


75 
So 




6% 


125 
151 
170 
238 
330 


7 


$x 


%y z 


TO 





Double Cylinder- Hoisting Engine. 



5 ■ 
5 ■ 

7 ■ 

sx. 

10 . 
12X. 
14 . 



6 


200 


6 


11. 8 


8 


160 


8 


12.6 


8 


160 


12 


19.8 


10 


125 


20 


24.2 


10 


125 


30 


33-6 


12 


no 


40 


37-3 


12 


no 


50 


52.4 


15 


100 


75 


89.2 


18 


90 


100 


125- 



1,000 
1,650 

2, 500 
3,500 
6,000 

S,ooo 

[0,000 



150 

160 
250 
302 

340 

476 

660 
1,125 

1,537 



AIR FOR PUMPS AND MOTORS. 



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262 



COMPRESSED AIR AND ITS APPLICATIONS. 



To find the amount of air and pressure required to pump a 
given quantity of water a given height, find the ratio of diame- 
ters between water and air cylinders, and multiply the number 
of gallons of water by the figure found in the column for the 
required lift. The result is the number of cubic feet of free 
air. The pressure required on the pump will be found directly 
above in the same column. For example: The ratio between 
cylinders being 2 to i. Required to pump 100 gallons, height 
of lift 250 feet. Find under 250 feet at ratio 2 to i, the figures 
2. 1 1 : then 2. 1 1 X 100 = 211 cubic feet of free air for the time 
required to lift the water, or per minute for both water and 
air. The pressure required is 34.38 pounds. 



TABLE XXXVII. 



Volume of Air and Pressure Required to Drive 
Direct-Acting Steam Pumps. (F. C. Weber.) 



a 


Gauge Pressures in Pounds 
Square Inch. 


PER 


Cubic Feet of Free Air per Minute to 
Lift One Gallon of Water. 


is+j 


Ratio 


>fCy 


linder Diameter 


s. 


Ratio of Cylinder Diameters. 


■a 

X 






is 

















a 


o 

•37 
•42 
•47 
•53 
• 58 
.63 
.68 
•75 
.82 
■95 
1.08 
1.22 
1.37 
1.64 
1.92 




• 53 

• 58 

• 65 
.70 

• 75 
•79 
.87 
.91 

1.06 
1.20 
1.32 
i-47 
i-75 
2.00 
2.28 
2.57 
2.88 



St 








o 




6 
11 
16 
21 
26 
3i 
36 
42 
47 
52 
65 
78 
90 
105 












.22 

.28 

•33 
.38 

• 44 
.49 
•54 
.61 
.66 

• 72 
.86 

1. 00 
1. 12 
1.28 


72 


• 94 
•99 
1.03 
1. 1 1 
I-I5 
1.20 
i-33 
1.50 
1.63 
i-75 
2.06 
2.31 
2-57 
2.87 
3-13 
3-42 
4.00 
4-58 
5-15 


1.67 
1.88 
2.00 
2.14 
2.41 
2.68 
2-95 
3.22 
3-48 
3.82 
4-35 
5.00 
5- 5o 
6.00 
6.70 






7 
10 
13 
17 
20 
23 
26 
30 
34 
42 
50 
58 
67 
83 
100 














30 
40 
5o 
60 


7 
9 
12 

14 

16 

18 
21 
23 
29 
35 
40 
46 
58 
68 
80 
92 
105 












7 
9 
10 
12 

14 

15 
17 
21 
25 
30 
34 
42 
50 
58 
67 
75 
85 
100 










7 
8 

9 
11 
12 

13 
16 
20 
23 
26 
33 
39 
45 
52 
58 
65 
78 
92 
105 






I 

I 
I 
I 
I 
I 
2 
2 
2 
2 
3 

3 


79 
82 
88 
95 
98 
05 
18 
3i 
47 
60 
86 
12 

39 
68 

94 
27 
76 










70 
80 














QO 














125 
150 
175 
200 
250 
300 
35o 
400 
45o 
500 


10 
13 
15 
17 
21 
25 
29 
33 
37 
42 
5o 
60 
67 
75 
85 


9 
10 
12 
15 
17 
20 
23 
26 
29 
35 
42 
47 
52 
58 


2.31 

2.40 
2.60 
2.89 

3.08 

3-37 
3.66 
3-95 
4.24 
4.80 
5-5o 
5-9 6 
6.45 
7.00 




























800 










900 











































AIR FOR PUMPS AND MOTORS. 263 

To find the quantity of free air required per minute, in a 
direct-acting steam pump, to raise a given number of gallons of 
water through a given head, divide the diameter of air cylinder 
by the diameter of water cylinder, and under the heading of 
this ratio in above table and to the right of the given head or 
lift find the cubic feet of free air per gallon required per min- 
ute ; this constant multiplied by the total number of gallons to 
be lifted will give the quantity of free air required. The gauge 
pressure for the corresponding conditions can be found in a sim- 
ilar manner under the heading of gauge pressures. 

In the above table of pressures an allowance of 1 5 per cent 
has been made for pump friction, and in the table of volumes 
1 5 per cent has also been allowed for clearance losses and leak- 
age. If the air is reheated before admission to air cylinder the 
quantity may be reduced in proportion to the ratio of absolute 
temperatures. For compound pumps the consumption may be 
assumed at 75 per cent of the best results of the above table. 

To find the amount of air required to drive any steam pump 
under any head of water : Divide the diameter of the air cylin- 
der by the diameter of the water cylinder, find the ratio in the 
first column of Table XXXVIII., follow the line of figures to the 
right until the column is reached which is headed by the head 
of water to be pumped against. At this point will be found a 
constant which, multiplied by the area of the air piston in 
square inches, will give the cubic feet of free air consumed by 
the pump per minute, at 100 feet piston speed per minute. 

AIR VOLUMES USED IN ENGINES AND MOTORS. 

The present increasing demand for the use of compressed 
air as a motive power necessarily involves the use of intricate 
mathematical formulae for estimating relative sizes of compres- 
sors and air engines. 

Quite a number of these formulae have been worked out to 
cover average practical conditions and are daily serving a very 
useful purpose in the form of tables. 



264 



COMPRESSED AIR AND ITS APPLICATIONS. 




































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AIR FOR PUMPS AND MOTORS. 



265 



A very intricate formula is the one based upon the use of 
free air per minute per indicated horse power in an air engine, 
and as a problem is often stated in terms of the I. H. P. of the 
motor — to find the quantity of free air per minute required; the 
following table will facilitate computations of this kind and is 
in such shape that it will not require any extended knowledge 
of mathematics : 

TABLE XXXIX.— Air Used in Cubic Feet Free Air per Minute, per 
I. H. P. in Motors (Without Reheating). 



Oifcj 


Gauge Pressures. 


O 3 


3°- 


40. 


5°-. 


60. 


70. 


80. 


90. 


100. 


no. 


125. 1 150. 


r 


23-3 


21.3 


20.2 


19.4 


1S.8 


18.42 


18.10 


17.8 


17.62 


17.40 17.05 


3 


18.7 


17.1 


16. 1 


15-47 


15-0 


14.6 


14-35 


14-15 


13.98 


13.78 i 13.50 




17-85 


16.2 


15-2 


14.50 


14.2 


13-75 


13-47 


13-28 


13.08 


12.90 


12.60 


1 


16.4 


14-5 


13-5 


12.8 


12.3 


n-93 


ii. 7 


11.48 


II.30 


11. 10 


10.85 


1 


i7-5 


15-2 


12.9 


11.85 


11.26 


10.8 


10.5 


10.21 


I0.02 


9.78 


9- 50 


¥ 


20.6 


x 5 .b 


13-4 


13-3 


11.40 


10.72 


IO.31 


10. 


9-75 


9.42 


9.IO 



As will be seen from the table, the only data required are the 
guage pressure and point of cut-off; having those two items 
given, we find from the table the free air required per I. H. P., 
and it will only be necessary to multiply this amount by the 
total I. H. P. of the motor to determine the total quantity of 
free air required and consequently the size of an air compressor 
to furnish the air. 

These figures do not take account of clearance, but it will 
be an easy matter to add the per cent of clearance after having 
determined the total amount of free air required. 

It will also be noticed that the free air consumption is based 
upon the use of cold air, i.e., initial temperature of air at 6o° 
F. In case reheating is resorted to there will be a correspond- 
ing decrease in the amount used depending upon the tempera- 
ture of air at admission to motor, and will be proportional to 



60 = 520 F. absolute tempera- 



T 
the ratio of — 2 where T„ =460 

ture and T 3 = 460 -|- temperature of air at admission to motor. 



266 COMPRESSED AIR AND ITS APPLICATIONS. 

Thus if the air is reheated to 300 F., the quantity in the 

table will have to be multiplied by "L — 4 = -^~ = -684. 

460 + 3°° 7 6 ° 

A further use of this table is to find the most economical 

point of cut-off for gauge pressures from 30 pounds to 150 

pounds per square inch. This fact is apparent from a study of 

each vertical column ; thus, at 60 pounds pressure, the lowest 

consumption of free air per I. H. P. is at \ cut-off, while a 40 

pounds pressure will work most economically at \ cut-off. 

— F. C. Weber in " Compressed Air." 

METER MEASUREMENT OF COMPRESSED AIR. 

The renting of air power caused by the rapidly extending use 
of compressed air requires, for measuring the quantity used by 
an air tenant, a means that is reliable within a small fraction of 
error. The measurement of water power is well established, 
but the measurement of steam power, except by the indicator, 
is but little practised by a meter. 

The needed measurements of the flow of natural gas to con- 
sumers at pressures beyond the capacity of the ordinary gas 
meter has led to the construction of a meter suitable for the 
measurement of the flow of compressed air for any pressure up 
to 500 pounds per square inch. The Equitable Meter Com- 
pany, Pittsburg, Pa., have made a study of meters for com- 
pressed air for a number of years with successful results. Their 
meters, which we illustrate, are made in five sizes as follows: 
10, 20, 30, 40, and 50 thousand cubic feet maximum capacity 
per hour. 

The method of measurement is by the amount of air in 
cubic feet at the pressure at which it passes through the meter, 
no matter if the air pressure is 1 pound or 100 pounds to the 
square inch ; and then, to find the total volume of free air passed, 
the volume of compressed air will have to be reduced into a 
volume of free air. 



MEASUREMENT OF COMPRESSED AIR. 



267 



This may be readily done by multiplying the meter index 
measurement in cubic feet by the ratio of isothermal compres- 
sion in column 3, Table XVII. , in this work. There is very 
little friction in the meter mechanism, amounting to only about 
one ounce absorption in pressure under any pressure passing 
through the meter. The meter is also provided with a relief 




FIG. 79 —THE AIR METER. 

valve to guard against wreckage of the meter mechanism by a 
sudden change of pressure on its two sides by accident. 

As the installation of compressed-air central plants for dis- 
tributing power is gaining daily in importance, the problem of 
measuring the amount of compressed air at certain pressures 
used by any consumer confronts not only the central plant own- 
ers, but also the consumer. The consumer should know how 
much air he uses in order to know that he is charged reason- 
ably for it, and the central plant owners must also know how 
much every consumer uses in order to avoid abuse and to as- 
certain whether the plant is operated on a paying basis. 



268 COMPRESSED AIR AND ITS APPLICATIONS. 

Thus the central plant owners, having a main supply pipe 
which may be branched off for distributing to mines or manu- 
facturing establishments, will find the necessity of installing 
meters and other apparatus which cannot be tampered with, 
and which at the end of each month will be able to give not 
only themselves, but also the consumer, proper data from which 
the bills for the month can be figured. 

The only way properly to determine the amount of com- 
pressed air used by any single consumer is to determine the 
amount of free air, which, if multiplied by the mean average 
pressure, will give the total amount of energy furnished. 

The next question of importance to be considered is for both 
producer and consumer to know that the air pressure is as 
steady as possible, and sufficient to run the apparatus to be 
operated by compressed air, as - there would be no use for a 
consumer to pay for a larger volume of compressed air at 50 
pounds pressure should he require 80 pounds pressure, as a 
large quantity of air at a low pressure would not do his work ; 
thus it would be necessary to install a compressed-air-pressure 
recording gauge in connection with each meter, and at the end 
of the month the mean average pressure could be figured ; and 
this, multiplied by the number of cubic feet of free air, the 
product representing the energy furnished, would enable both 
producer and consumer to settle upon the amount to be paid. 

The problem has been explained clearly enough, but it may 
be added, however, that it would always be advisable to install 
a small receiver next to the meter, and that the pressure record- 
ing gauge should be connected with this receiver; this, not 
only to avoid vibration of the recording finger, but also to pre- 
vent any shock to the meter. 

It should be noted also that a consumer situated far away 
from the central power plant should pay more per unit of 
energy than one near by, for the reason that the friction in 
long pipes amounts to a certain percentage of power, and that 
a long pipe line is more subject to leaks and requires more at- 
tention than a short one. 



Chapter XVIII. 



AIR COMPRESSORS 



AIR COMPRESSORS. 

One of the earliest compressed-air devices was the trompe 
or hydraulic air blast for forges. Its capacity was sufficient for 
the wants of the times, which made it the principal means for 
furnishing a steady blast for the Catalan forges of the early 




Fig. 80.— the trompe. 



years of the iron age. It could produce a pressure from an 
ounce to one pound or more, according to the height of the 
water shaft and the depth of the water seal. In the trompes of 
the best construction the water seal was a sliding gate which 
could be operated to produce any desired pressure within the 
range of the apparatus. Its operation was as follows (Fig. 80): 
the falling column of water draws in air through the small in- 
clined orifices as shown by the arrows, carrying it into the 



272 



COMPRESSED AIR AND ITS APPLICATIONS. 



reservoir where it separates, and is discharged through the 
tuyere pipe. The outlet discharges the water through an in- 
verted siphon, carried high enough to balance the air pressure. 
In the principles of the trompe is found a correspondence 
and suggestion of the experiments made by J. P. Frizell in 




FIG. Si. — the frizell system. 



1877, and since carried out on a larger scale by C. H. Taylor 
in the practical hydraulic air compressors at Magog, Quebec, 
and at Ainsworth, B. C. 

Many experiments have been made to compress air by the 
direct and injector system for small quantities, by the use of 
water under pressure from city water supply. 

By direct pressure it requires an equal quantity of water to 
the volume of free air compressed to nearly the same pressure 
as the water. By the injector system, the only available ex- 
periments are those of M. Romally, in France, who found that 
with 35 feet head only 46 per cent of the volume of the water 
used was equal to the volume of free air at a pressure of 21 
pounds per square inch; thus realizing an air pressure of 138 
per cent of the hydraulic head and less than one-half the vol- 
ume, an efficiency of about 63 per cent. 

Mr. Frizell's experiments involved a large outlay in cost of 
plant, and where there is a moderate water-fall and plenty of 
water this is no doubt the cheapest working method of com- 
pressing air i The general idea of Mr. Frizell was to utilize a 



AIR COMPRESSORS. 



2 73- 



high water-fall with built-up shafts and air chamber, or with 
a low water-fall to sink shafts with an air-gathering chamber 
at the bottom and air pipe leading to the surface as shown in 
Fig. 81. The entrance at A in the cut was a circular hollow 
dam with a conical inlet. The annular chamber under the dam 
communicated with the outer air and was perforated, so that the 
falling water drew down the air and by its velocity carried the 
air to the receiving chamber below. This suggestion and ex- 
periments lay in abeyance under the Frizell patent for many 
years, and was supplemented by a similar patent to Mr. George 
Waring. The efficiency in Frizell's early experiments was 26 
per cent of the fall of water used in the apparatus. Later im- 
provements by him raised the 
efficiency to 52 per cent with 
a head of 5 feet. 

The hydraulic compressor 
system of Mr. Taylor is il- 
lustrated in Figs. 82 and 83, 
in which a large number of 
small air tubes are distributed 
around an annular water inlet 
to the down-flow pipe. One 
of its several forms of con- 
struction is shown in Fig. 82, 
and more fully illustrated in 
Figs. 84 and 85. 

A number of air tubes, 
c, c, terminate at the conical 

entrance of the down-flow pipe, B, at a, a, Fig. 82. A supply of 
water to the chamber A, A, and its flow down the pipe, draws 
air through the small pipes, carrying it down to the separating 
tank, c, c, where it is liberated at the pressure due to the hy- 
drostatic head. The air is delivered through a pipe, as shown 
in the cut, and the water rises through a pi; e or open shaft to 

the tail race. 
18 




FIG. 82.— THE TAYLOR HYDRAULIC AIR COM- 



2 74 COMPRESSED AIR AND ITS APPLICATIONS. 

The compressor as erected at Magog, Quebec, gives in air 
power 62 per cent of the water power used and delivers 155 
horse power in compressed air at 52 pounds gauge pressure. 




Fig. 83.— hydraulic air compressor. 
Magog, Quebec. Air head section. 



A most remarkable feature of this system is that, notwith- 
standing that the air is compressed by the weight of the water 
and in actual contact with it, the air so compressed is delivered 



AIR COMPRESSORS. 275 

in the receiver and thence to the transmission pipe drier than 
when drawn in from the atmosphere. 

At first sight this would seem impossible, but it is well 
known that in a high temperature moisture is held longer in 
air than in a lower temperature, hence the contact of the air 
globules with the cold water keeps down the temperature usu- 
ally caused by the compression of air, and the atmospheric 
moisture held in the globules condenses, as it were, on the 
walls of these globules, and at the point of separation the air 
and water are absolutely separated, leaving the air all ready . 
for distribution at the same temperature as the water it has 
just left, and drier than when first taken in through the small 
air pipes. 

Another feature is that the power of the water can be con- 
verted into compressed air at any pressure per. square inch, 
giving the same efficiency at either high or low pressure with a 
far less loss of energy than by any other process of transform- 
ing a water power into transmittable force, and with unvarying 
pressure. 

Should the volume of air taken down be greater than that 
being used, it accumulates in the receiver until it forces the 
water below the lower end of the receiver, and the surplus 
passes up with the return water, thereby forming a perfectly 
automatic safety-valve, without requiring any attendance what- 
ever. It will be observed that the material used in the con- 
struction of the down-flow pipe need only be of sufficient 
strength to carry the weight of water and pressure generated in 
the working head of the water 'power, as once it reaches the 
tail-race level the internal pressure is gradually neutralized 
from that point down by the pressure in the return water sur- 
rounding the down-flow pipe ; so that any pressure almost may 
be reached without increasing the strength of the down-flow 
pipe. The material for the down-flow pipe may be of iron, or 
wood hooped with iron, and the shaft may be constructed of 
the cheapest of timber; and as it is preserved by being con- 



276 



COMPRESSED AIR AND ITS APPLICATIONS. 




|— — — \hl~rr ~ 

Sectional View 
Fig. 84.— hydraulic air compressor. 
Magog, Quebec. Air chamber section. 



AIR COMPRESSORS. 



277 



stantly in the water, there is practically no limit to its dura- 
bility. 

By this system low falls, otherwise useless, may be utilized, 
and the same pressure obtained as from high falls, the horse 
power being determined by the diameter of the down-flow pipe, 
and the height and volume of water in the fall, while the press- 
ure depends solely upon the depth of the well or shaft; there- 
fore any desired pressure can be obtained. 

In the apparatus at Magog, Quebec, the receiver is suffi- 
ciently large in diameter to allow the air to rise to the surface 



Plan of Head Piece 




Fig. 85— plan of air tui 



of the water therein, from whence it is taken through the air 
pipe for transmission to be utilized as power or for other pur- 
poses. The water, being kept down by the pressure of the air, 
is forced out through the open bottom of the receiver and up 
the shaft around the down-flow pipe to the tail-race level. 

The compressor is so constructed as to permit of its being 
regulated to furnish any proportion — from one-third of its ca- 
pacity — using water proportionately with a like efficiency. 

By reference to the head section (Fig. 83) it will be noticed 
that the head piece is telescoped into the down-flow pipe, and 
raised or lowered by means of a hand-wheel on top, thus per- 
mitting the flow of water to be regulated, or to lift it above the 



278 COMPRESSED AIR AND ITS APPLICATIONS. 

water level and stop entirely the flow of air, the water being 
regulated by the head gate. 

Briefly stated, the air is compressed by the direct pressure 
of falling water without the aid of any moving machinery, and 
practically without expense for maintenance or attendance after 
installation. 

By this system any fall of water varying in working head 
may be utilized, and any pressure required can be produced 
and uniformly maintained up to the capacity of the water 
power, delivering the compressed air at the temperature of the 
water, and in a drier state than is possible by any known means 
of compression, thereby avoiding all loss by condensation or 
shrinkage by cooling of the air after compression. 

The water may be conveyed to the compressor by means of 
an open flume; or, as shown in the diagram, through a pipe 
supplying a tank or stand-pipe around the headpiece of the 
compressor, where it can attain the same level as the water in 
the dam or source of supply. 

Around the head-piece are placed a large number of small, 
horizontal air pipes, drawing their supply of air through larger 
vertical pipes, which extend above the surface of the water and 
open to the atmosphere. 

As the water enters the down-flow pipe and passes the ends 
of these small air pipes, it draws in the air in the form of small 
uniform globules, which, becoming entangled in the descending 
water, are carried down to the receiver at the bottom of the 
pipe, compressing the air by the pressure of the water sur- 
rounding these globules until they reach the point of separa- 
tion. This pressure is maintained so long as there remains 
any air in the receiver chamber. 

The enlargement of the down-flow pipe at the bottom sec- 
tion was made to lessen the velocity of the water and air at that 
point, which was found to facilitate the separation of the air 
from the water by coalescing the small globules of air and the 
better separation at the deflecting plate below. The deflecting 



AIR COMPRESSORS. 



279 



plate prevents the plunge of the down-flowing water into the 
separating part of the tank and by its deflections gives the air a 
more ready separation from the water. By this arrangement 
no air was found in the water discharge pipe. 

In tests of efficiency it has been found that the gross power 
of the water passing through the compressor due to its natural 
fall was 158 horse power, of which 1 1 1 horse 
power was utilized in the work of air com- 
pression, giving an efficiency of 70 per cent 
of the gross power used. 

Later experiments indicate that an effi- 
ciency of 75 per 
cent may be ob- 
tained by a 
modification of 
the air inlet pipes and water head. 

In Fig. 86 is illustrated the Taylor 
hydraulic air-compressing plant at 
Ainsworth, B. C, which was estab- 
lished in a trussed tower in order to 
carry up the air head to a level with 
the flume, of which Fig. 86 represents 
the elevation and arrangement of the 
head. The available working head 
from the water level in the head stock 
to the tail race is 102 feet; the depth 
of the shaft is 210 feet, and the depth 
of the air chamber at the bottom of 
the shaft is 17 feet, from which the 
water closure of the down-flow tube 
leaves 200 feet as the available hydro- 
static pressure, which gives an air pressure of 87 pounds per 
square inch. The flume supplying water from Coffee Creek, 
1,350 feet distant, is 5 feet in diameter, of stave-barrel construc- 
tion. The tower head is also of wood staves, is 12 feet in 





— HYDRUALIC AIR COM- 
PRESSOR. 

Ainsworth, B. C. 



28o COMPRESSED AIR AND ITS APPLICATIONS. 

diameter and 20 feet high. The down-flow pipe is of the same 
construction, 2 feet 9 inches in diameter, widening slightly 
at the bottom to retard the velocity of the descending water 
and allow it to impinge upon a whorling cone that produces a 
circling current in the air chamber that facilitates the separa- 
tion of the compressed air from the water. The air rises to the 
top of the separating chamber and is delivered through a 9-inch 
pipe to the various branches for air distribution at the ground 
surface. A secondary pipe is carried from midway in the sepa- 
rating chamber to the surface above the tail race that seals the 
air space with water when the air is being used in excess of 




FIG. 87.— HARTFORD AIR COMPRESSOR. 

compression, and allows the air to escape when it accumulates 
and pushes the water surface below the mouth of the air pipe; 
thus making an air-pressure regulator within the limit of one- 
pound air pressure. 

The regulation of the air-inlet pipes, of which there, are 
about three thousand tubes, f-inch diameter and the conical 
adjutage, is made by raising or lowering the air pipes and cone 
by a screw and wheel, as shown in Fig. 86. The velocity of 
the water in the down-flow pipe is about 34 feet per second, 
and the velocity of the indraft of air is nearly the same. The 
air is received by the water in millions of globules, which in a 
great measure retain their individuality, gradually becoming 
smaller by the increasing water pressure until they are liber- 
ated in the air chamber below. 

The air intake is estimated at 5,000 cubic feet of free air 



AIR COMPRESSORS. 



per minute, and at 85 pounds pressure should develop nearly 
500 horse power. 

The air plant has a distributing system of over 11,000 feet 
of pipe of varying sizes in use in a number of mines. The air 
is unusually dry, and the drills and hoists have no trouble from 
frosted exhausts. 

The hydraulic air compressor of the L. E. Rhodes Com- 
pany, Hartford, Conn. (Fig. 87), consists of two displacement 
cylinders with alternating water 
valves to control the operation of the 
compressor. It operates by water 
pressure from any water-works sup- 
ply, and will compress an equal vol- 
ume of free air to the volume of 
water used, to nearly the same press- 
ure as the water supply. It is a 
most convenient apparatus for sup- 
plying compressed air for dental air 
tools, spraying, and for man} r uses 
where a small quantity of compressed 
air is required in experimental and 
laboratory work. In Fig. 88 is illus- 
trated the vertical differential com- 
pressor, in which a larger volume of air, in proportion to the 
water used, is obtained at lower pressure than that of the water 
by the differential area of the pistons. 

A direct-acting hydraulic air compressor was. used at the 
Mont Cenis tunnel, using a mountain stream giving a head of 
85 feet. A number of compressors were installed on this prin- 
ciple by Sommeiller, which gave satisfactory results at that 
time, owing to the favorable location of the mountain stream. 
This idea has been followed since by many patents on direct- 
acting hydraulic air compressors. The want of favorable loca- 
tions where high pressure and volume can be obtained has caused 
this system to be neglected. 




Fig. 88.— vertical compressor. 



282 



COMPRESSED AIR AND ITS APPLICATIONS. 




FIG. 89.— DARLINGTON COMPRESSOR. 



This was followed by the Darlington hydraulic piston com- 
pressor, illustrated in Fig. 89, which was designed somewhat 
after the model of the Sommeiller, using water for a piston, 
which was operated by a piston driven 
by a steam engine. It was much in 
use in France, Germany, and Belgium 
during the earlier period of air com- 
pression for practical work, 
but was soon superseded by 
the modern designs. Its 
action was as follows: A 
reciprocating piston in the 
water cylinder, G, produces an oscillating motion in the water 
of the two vertical cylinders, drawing in air through the flap 
valves at the side, and discharging the compressed air through 
the valves at the top. The water pipes, t, t, t, are to supply 
the place of water ejected through the air valve by delivering 
all the air compressed at each stroke of the piston. 

A further advance in air-compressor design seems to have 
been made in the model of the Dubois and Francois compres- 
sors, which was intended to improve on the slow work of the 
Sommeiller compressors by charging the cylinder with no 
more water than would fill the valve chambers, and inserting 
water jets for cooling the air dur- 
ing compression, and to supply 
the waste by carrying part of 
the water through the exit 
valves. 

In this design the practical 
operation and speed seemed a 
great advance over the former 
designs, and for a time seemed 

to take a leading place for air compression in France and Ger- 
many. 

In the mean time progress was being made in England and 




Fig. 90.— Dubois and francois com- 
pressor. 



AIR COMPRESSORS. 



283 



6utV v^Yi/ 



the United States by reducing the cylinder clearance, and with 
only a small spray for cooling effect and for balancing the un- 
equal effect of the steam impulse and 
the air resistance, when steam was 
used expansively and for its best 
economy. The first efforts were by 
placing the steam and air cylinder 
at a right angle and operating 
through angular cranks. This ar- 
rangement used in the Burleigh 
and early Ingersoll type is sketched 
in Fig. 91, in which the cylinders 
were set at 90 and the cranks at 30 




Fig. 91.— type. 







Fig. 92.— type. 



Ths plan was also used 
by Delavergne for ammonia com- 
pressors, and is still in use by the 
Frick Company and others for am- 
monia. 

Another form of construction by 
Rand and Waring was in use in 
1872, and is shown in sketch (Fig. 
92). The steam cylinder was 
placed over the air cylinders at an 
angle of 45 , and connected to a single crank. This form made 
a fairly compact arrangement of frame, and in a measure 
equalized the steam and air 
pressures. Davies in Eng- 
land also worked on these 
ideas and built compressors 
with cylinders at an angle of 
1 3 5 ° and connected to a single 
crank (Fig. 93). It was 
early perceived that an angu- 
lar position of the cylinders 

involved expensive construction and unsteadiness, and later ex- 
perience has proved that it is expensive in construction and 




Fig. 93.— type. 



284 



COMPRESSED AIR AND ITS APPLICATIONS. 



does not fully equalize the compression strains. This form of 
construction involves much greater weight and strength in the 
frame, all of which has been obviated in the later construction 
of straight-line compressors with the controlling power in a 
heavy fly-wheel and moving parts. 

Many efforts were made to equalize the power and resistance 
by constructing the air compressor on the crank-angle princi- 




VwKvaK \\v«- Mox\\<*v\tuwv a\ XWe V V^ V\ W\ 

Fig. 94.— direct compression. 



pie, putting the cranks at various angles, and by direct-line 
positions of steam and air cylinders, and this is yet in practice 
for compressors in ammonia refrigerating apparatus. 

Fig. 94 shows the true relation of pressures when the steam 
and air pistons are on a direct or straight-line piston rod. 

It is evident that an air compressor which has the steam 
cylinder and the air cylinder on a single straight rod will apply 
the power in the most direct manner, and will involve the sim- 
plest mechanics in the construction of its parts. It is evident, 
however, that this straight-line, or direct, construction results 
in an engine which has the greatest power at a time when there 
is no work to perform. At the beginning of the stroke, steam 
at the boiler pressure is admitted behind the piston ; and as the 
air piston at that time is also at the initial point in the stroke, 
it has only free air against it. The two pistons move simulta- 
neously, and the resistance in the air cylinder rapidly increases 
as the air is compressed. To get economical results it is, of 
course, necessary to cut off in the steam cylinder, so that at the 
end of the stroke, when the steam pressure is low, as indicated 



AIR COMPRESSORS. 285 

by the dotted line (Fig. 94), the air pressure shall be high, as 
similarly indicated. The early direct-acting compressor used 
steam at full pressure throughout the stroke. The Westing- 
house pump, applied to locomotives, is built on this principle, 
and those who have observed it at work have perhaps noticed that 
its speed of stroke is not uniform, but that it moves rapidly at 
the beginning, gradually reducing its speed, and seems to labor 
until the direction of stroke is reversed. Such construction is 
admitted to be wasteful, but in some cases, notably that of the 
Westinghouse pump, economy in steam consumption is sacri- 
ficed to lightness and economy of space. 

The alternating pressures in a steam-driven compressor 
with a single air and steam cylinder are largely overcome in 
a duplex compressor, as shown by the two positions of the 
steam and air pistons in the upper section of the cut (Fig. 95), 
when moving in the same direction as shown by the direction 
of the two cranks at right angles on the shaft, and when the 



Fig. 95.— action of the duplex air compr 

pistons are moving in opposite directions as shown by the posi- 
tion of the cranks in the lower section of the cut. 

The conditions of equalization of pressures are shown by 
commencing at that point of the stroke indicated in the top sec- 
tion. The upper right-hand steam cylinder, having steam at 
full pressure behind its piston, is doing work through the angle 
of the crank shaft upon the air in the lower left-hand cylinder. 
At this point of the stroke the opposite steam cylinder has a 



286 COMPRESSED AIR AND ITS APPLICATIONS. 

reduced steam pressure and is doing little or no work, because 
the opposite air cylinder is beginning its stroke. Referring 
now to the lower section, it will be seen that the conditions are 
reversed. One crank has turned the centre, and that piston 
which in the upper section was doing the greatest work is now 
doing little or nothing, while the labor of the engine has been 
transferred to those cylinders which a moment before had been 
doing no work. 

There are some advantages in the duplex construction, and 
some disadvantages. The crank shafts being set quartering, 
as is the usual construction, the engine may be run at low 
speed without getting on the centre. Each half being com- 
plete in itself, it is possible to detach the one when only half 
the capacity is required. The power and resistance being 




Fig. 96.— direct acting. 

equalized through opposite cylinders, large fly-wheels are not 
necessary. Strange to say, the American practice seems to be 
to attach enormous fly-wheels to duplex air compressors. It is 
difficult to justify this apparently useless expense in view of 
the facts shown in Fig. 95. A fly-wheel does not furnish 
power, nor does it add to the economy of an engine except in 
so far as it enables it to cut off early in the stroke, and to 
equalize the power and resistance. In other words, a fly-wheel 
is not a source of power, and in many cases it is only a means 
by which is accomplished equal rotative speed. It takes power 
to move matter, and, assuming that other conditions are equal, 
every engine that carries a fly-wheel that is larger than is 
necessary consumes a certain number of foot-pounds in turn- 
ing so much metal around through space. Were it possible to 
cut off at the same point and rotate as positively without a fly- 



AIR COMPRESSORS. 



287 



wheel, it would be done away with entirely. Some straight- 
line air compressors are so constructed that the momentum of 
the piston and other moving parts is nearly sufficient to equal- 
ize the strains without a fly-wheel ; but the fly-wheel is there 




Fig. 97.— straight line. 



because it insures a definite length of stroke, and because it 
enables us to operate eccentrics and to regulate the speed of the 
engine uniformly. 

Objections to the duplex construction are : The strains are 
indirect, angular, and intermittent. It is necessary therefore 
to largely increase the strength of parts ; to add a crank shaft 
of larger diameter with enormous bearings, and to build ex- 
pensive and very secure foundations. Should the foundations 
settle at any point, excessive strains will be brought upon the 
bearings, resulting in friction and liability to breakage. A 
steam engine meets with a resistance on its crank shaft that is 




Fig. 98.— air-brake compressor. 



comparatively uniform throughout the stroke, while an ail 
compressor is subject to a heavy maximum strain at the end 
of the stroke ; hence the importance of direct straight-line con- 
nection between power and resistance. 



288 



COMPRESSED AIR AND ITS APPLICATIONS. 



The friction loss on a duplex compressor seldom gets lower 
than 15 per cent, while straight-line compressors show as low 
a loss as 5 per cent. 

To illustrate the leading types of the modern direct-acting 
compressors, the following sketch cuts are representative of 

some of the leading models: 

Fig. 96 is an elevation of 
the Clayton air compressor 
with a yoke-frame connecting 
rod in line with the piston 
rods, the crank and connect- 
ing rod operating between 
the rods of the yoke frame. 
Fig. 97 represents the 
outline of the " Bennett " straight-line compressor, showing a 
lever valve gear, operated by direct connection from the lever 
to the eccentric by a link. 

In Fig. 98 is represented a vertical section of a unique 
construction in air compressors in which a double-acting steam 
cylinder operates two single-acting air cylinders through the 
medium of toggle beams, each beam having two stationary 




FIG. 99.— THE NORWALK, 




FIG. 100.— TAN' HI- M CORLISS, 



pivots and being linked to the beam for producing parallel mo- 
tion of the piston rods (New York Air Brake Company model). 
In Fig. 99 is given a sketch of a. compound straight-line 
steam-actuated air compressor with an intercooler connecting 
the low- and high-pressure cylinders (type of the Norwalk Iron 
Works). 



AIR COMPRESSORS. 289 

The attachment of the air cylinder tandem to a Corliss en- 
gine is one of the improvements of late years in the line of 
economy, and for large outputs of compressed air has no equal 
in operative duty. 

In Fig. 100 is illustrated a vertical sketch of a single Corliss 
tandem-operated air compressor, and in Fig. 10 1 a duplex com- 
pressor of the slide-valve gear pattern in plan and elevation 
(the piston inlet type of the Ingersoll-Sergeant Drill Company). 




Fig. ioi.— duplex compressor. 



In Fig. 102 is a sketch illustration of a straight-line piston 
inlet compressor in vertical section and plan, as operated by a 
Pelton water-wheel (type of the Ingersoll-Sergeant Drill Com- 
pany, which will be described in detail further on). 

In Fig. 103 is represented a detailed section of the cylinders 
of a high-pressure air or gas compressor of the Ingersoll-Ser- 
geant Drill Company, in which both pistons are single-acting, 
with water-jacketed cylinders. The forward motion of the 
pistons allows the air entering at the port A to be drawn 
through the annular valve in the large piston to be compressed 



290 



COMPRESSED AIR AND ITS APPLICATIONS. 



by the back stroke, and transmitted to the compression side 
of the high-pressure piston through a direct outside pipe or 




Pig. 102.— pelton wheel compressor. 



through an intercooler. The lettered parts are plainly recog- 
nized and need no special explanation. The initial air cylinder 
is made of a size to meet the requirement of full volume to the 
high-pressure cylinder and to equalize the machine strains due 




Fig. 103.— section of the compound air cylinder. 



to both half-strokes, or one revolution of the fly-wheel. The 
single-acting principle is conducive to efficiency in jacket 
cooling. 



Chapter XIX. 



AIR COMPRESSORS— Continued 



AIR COMPRESSORS. 

{Continued.) 
AIR COMPRESSORS OF THE INGERSOLL-SERGEANT TYPE. 

The early compressors of the Ingersoll-Sergeant Drill Com- 
pany were made with solid pistons and inlet and exit valves in 
the heads of the cylinders. Gradual improvements in their 
long experience have led to higher development in the economy 
of air compression. The Meyer variable cut-off and the air 
pressure controlling device applied to the steam cylinder, with 
a large reduction in the clearance of the steam cylinder, to- 
gether with the straight-line effect, have brought the steam end 
of the compressor to a perfect action. Improvements in the 
air cylinder have kept even pace, and among them we illustrate 
the piston inlet air cylinder (Fig. 105), and the annular valve 
at G in the cut. The air is taken in through a hollow piston 
rod at E and into the hollow piston, and delivered to the cylin- 
der each way through an annular steel valve that opens and 
closes automatically by its own momentum derived from the 
motion of the traversing piston ; requiring no springs to control 
its operation. It has a large area of opening with but a small 
throw of valve, thus quickly opening a large supply port, en- 
abling the compressor to run at high speed without a reduction 
in efficiency and with safety to the moving parts. As the travel 
of the valve is only about one-quarter of an inch, it does not 
move far enough to acquire sufficient momentum to injure 
itself or its seat, and remains perfectly tight till worn out. It 
is as positive in its action and as indestructible as a piston ring. 
The discharge valves are of the cylindrical poppet type, sliding 



294 



COMPRESSED AIR AND ITS APPLICATIONS. 





Fig. 105.— the piston inlet. 



AIR COMPRESSORS OF THE INGERSOLL-SERGEANT TYPE. 295 

in screw caps with helical springs. Cylinder and heads are 
water-jacketed. 

In Fig. 106 is illustrated a late improvement in the valve 
arrangement of the air cylinders of this company. The intake 
valves are made large and of light weight, and so protected by 
the overlap of the cylin- 
der heads that they can- 
not be drawn into the 
cylinder by the breakage 
of a stem. The vertical 
movement of all the air 
valves insures even wear 
on their seats. This po- 
sition of the valves enables a full water-jacketing of the heads 
of the cylinders. 

In Fig. 107 is illustrated an elevation and plan of the piston- 
inlet belt compressor of this company, showing the swivel-block 
cross-head for equalizing any irregularity in setting up the 
connecting-rod brasses, a special feature of the transmitting 
gear of these compressors. 

In Fig. 108 is illustrated the unloading device by which a 
uniform air pressure is kept in the receiver and pipe line. It 
is automatic, requiring no attention from the engineer further 

than to set it for the re- 
quired pressure. A 
weighted piston safety- 
valve is attached to the air 
cylinder, and connected 
with the air receiver, and 
with a discharge valve on 
each end of the air cylin- 
der, also with a balanced 
throttle valve in the steam 
pipe. When the pressure of the air gets above the desired 
point in the receiver, the valve is lifted and the air is exhausted 




FIG. 106 —VERTICAL VALVE CYLINDER. 



296 



COMPRESSED AIR AND ITS APPLICATIONS. 



from behind the discharge valves, thus letting the compressed 
air at full receiver pressure into the cylinder at both ends, and 
balancing the engine. At the same instant the compressed 
air is exhausted from the piston connected with the balanced 
steam valve and the steam is automatically throttled, so that 
only enough steam is admitted to keep the engine turning 
around, or to overcome the friction, no work being done. 

When the compressor is unloaded, it is evident that the 
function of the air piston is merely to force the compressed air 




Fig. 107.— the piston inlet belt compressor. 



through the discharge valves and passages from one end to the 
other until more compressed air is required, this being indi- 
cated by a fall in the receiver pressure. The weighted valve 
now closes and the small connecting pipes are instantly filled 
with compressed air ; the steam valve automatically opens and 
the compression goes on in the regular way. The unloaded in- 
dicator card (Fig. 109) shows the air-pressure conditions under 
the control of the unloading device by the black lines, and the 
normal compression by the dotted lines. Another function 
of this device is to prevent the compressor from stopping or 



AIR COMPRESSORS OF THE INGERSOLL-SERGEANT TYPE. 297 

getting on the centre. Direct-acting compressors are liable 
to centre when doing work at slow speed. 

In Fig. 1 10 is illustrated a pair of straight-line air compres- 
sors placed side by side as a duplex compressor, operated from 
a high water-head with double nozzles and Pelton wheels. The 




size of the Pelton wheels for direct action upon the air pistons 
is made to meet the requirement of a half speed for spouting 
velocity of the water at the nozzles to correspond to the re- 
quired speed of the compressor. This plant was sectionalized 
for transport on mule-back, and operated in Peru, South 
America. 



COMPRESSED AIR AND ITS APPLICATIONS. 



=. 



—Air 

Pressure 
line 
10 lbs. 



■I'--'- 



FIG. 109 —INDICATOR CARD OF THE UNLOADED AIR CYLINDER. 




AIR COMPRESSORS OF THE INGERSOLL-SERGEANT TYPE. 



2 99 



•■.' ■i'i-Sfc 




* 5 
« .3 



h be 



300 



COMPRESSED AIR AND ITS APPLICATIONS. 




-DUPLEX STEAM DRIVEN AND COMPOUND AIR CYLINDER COMPRESSOR WITH INTER- 
COOLER IN BASE. 



AIR COMPRESSORS OF THE INGERSOLL-SERGEANT TYPE. 301 




302 



COMPRESSED AIR AND ITS APPLICATIONS. 




AIR COMPRESSORS OF THE INGERSOLL-SERGEANT TYPE. 303 




:1 . til 



Fig. 115.— battery of duplex corliss air compressors. 
Corliss type of air valves with positive motion. 



304 COMPRESSED AIR AND ITS APPLICATIONS. 




Pig. 116.— four-stage air compressor. 



Twelfth Avenue and Twenty-fourth Street, New York City, Metropolitan Street Railway 

Company. 



AIR COMPRESSORS OF THE INGERSOLL-SERGEANT TYPE. 305 



A THOUSAND-HORSE-POWER AIR COMPRESSOR. 

The four-stage air compressor of the Ingersoll-Sergeant 
Drill Company that gives power to the cars of the Metropolitan 
Street Railway Company of New York is probably the largest 




' ■ ' ■". •■ '■: : - '■ ; ' . ', ■ - ' 



FIG. 117. —THE VERTICAL HIGH-PRESSURE FOUR-STAGE AIR COMPRESSOR. 

Front view. 



air compressor yet made in any country, and embodies charac- 
teristics in design and construction far in advance of ordinary 
practice. 

The steam power of the compressor consists of a duplex 
vertical cross compound engine built by the E. P. Allis Com- 
pany, Milwaukee, Wis., having cylinders 32 and 68 inches 



3°6 



COMPRESSED AIR AND ITS APPLICATIONS. 



diameter by 60 inches stroke, provided with Reynolds-Corliss 
valve gear. With steam pressure of 150 pounds' and 40 revolu- 
tions per minute, it is equal to 1,000 horse power. The fly- 
wheel is 22 feet in 
diameter, and weighs 
60 tons. The engine 
is mounted upon 
brick piers, and di- 
rectly beneath each 
steam cylinder is 
placed a pair of air 
cylinders, tandem, 
and connected to the 
steam cylinder cross- 
heads by a yoke 
frame. The low- 
pressure air cylinder 
and first interme- 
diate are 46 and 24 
inches diameter 
placed tandem ; sec- 
ond intermediate and 
high-pressure cylin- 
ders are 14 and 6 
inches diameter re- 
spectively, also tan- 
dem, and the stroke the same as the engine, 60 inches. All the 
air cylinders are single-acting. 

The free-air capacity per revolution is 56.73 cubic feet; ca- 
pacity at 40 revolutions 2,269 cubic feet, and the free-air capac- 
ity at 60 revolutions is 3,404 cubic feet. The approximate 
pressure in the first cooler is 40 pounds, the second 180 pounds, 
and in the third 850 pounds, the final approximate pressure in 
the after-cooler being 2,300 pounds. 

The compressor pistons are arranged in pairs vertically in 




W^W8B^^S^^M&Sb. % ,I : z - 



Fig. 118.— four-stage high-pressure air compressor 



AIR COMPRESSORS OP THE INGERSOLL-SERGEANT TYPE. 



307 



line beneath the steam cylinders, the initial and first interme- 
diate air cylinder being below the low-pressure steam cylinder, 
while the second intermediate and high-pressure air cylinders 
are below the high-pressure steam cylinder. Motion is trans- 
mitted from the steam-engine cross-heads through distance rods 
for each cross-head to a cross-head attached to the air- cylinder 
piston rods. 

The inlet and discharge valves of the initial air cylinder are 
of the "Mechanical" type and of a special design. Air is ad- 
mitted to the top of this cylinder through a supply pipe and 
leaves the cylinder through a pipe, by which it is conducted to 
the first intercooler. 
From the cooler the 
air flows through a 
pipe to the lower end 
of the first interme- 
diate air cylinder, 
from which it passes 
through a pipe to the 
second intercooler. 
From here it passes 
through a pipe to 
the upper end of the 
second intermediate 
cylinder, from which 
it passes to the third 
cooler, and from here 
through a pipe to 
the lower end of the 
high-pressure cylin- 
der, and from this 
through a pipe to the final aftercooler, from which it is led 
through the outlet to the storage bottles. From this it will be 
seen that the air passes through the upper end of the low- 
pressure cylinder, lower end of the first intermediate cylinder, 




9. -PLAN, FOUR-STAGE HIGH-PRESSURE AIR COM- 
PRESSOR. 



308 COMPRESSED AIR AND ITS APPLICATIONS. 

upper end of the second intermediate cylinder, and lower end 
of the high-pressure cylinder, and in its passage between each 
travels through one or. the other of the coolers. 

The intercoolers employed are of two different designs. The 
two coolers for the lower pressures consist of a shell enclosing 
a nest of vertically arranged cooling pipes through which the 
air passes going from one cylinder to the other ; the coolers for 
the higher pressures consist of a shell enclosing a pipe coil, the 
air passing through the coil from one cylinder to the other. 
In providing a cooler for the lower pressures, where great cool- 
ing surface is required on account of the large volume of air to 
be cooled, it was considered proper to provide tubes, but in 
dealing with the cooler for the higher pressures, coils were 
substituted so as to dispense with as many joints as possible. 
The coolers are arranged so that in case of a leakage of air 
from the cooling pipes into the shell or casing, this air rises with 
the circulating water up to the operating floor of the engine 
room and is discharged through a sight discharge pipe under 
the immediate care of the engineer. All the piping from the 
first air cylinder and through the entire compressing plant is 
made of copper. 

What may be called an auxiliary governor controlled by air 
pressure is provided to act upon the governor of the steam 
engine. This consists of a weighted lever which is operated 
upon by a small piston, which in turn is actuated by the air 
pressure. If for any reason the pressure should become exces- 
sive the lever is lifted, when it opens a valve admitting air to a 
device on the governor so designed as to reduce the steam sup- 
ply, and to all practical purposes throttles the engine. 

Compressed air for the purpose of storage and traction by 
the high-pressure system consists in reservoir capacity due to a 
collection of steel bottles, connected together in series or by 
manifolds, whereby the different sections of storage can be cut 
out from one another. 

In the storage system erected at the Twenty-fourth Street, 



COMPRESSED-AIR STORAGE. 3O9 

New York City, compressor station there are about 600 bottles. 
These bottles are all tested to a pressure of 4,500 pounds per 
square inch, and are used to store air at a pressure of 2,500 
pounds per square inch. There is no wear and tear on these 
storage bottles other than can be made good by painting from 
time to time. The storage bottles are connected together with 
proper pipes and valves, and communicate with several charg- 
ing stands in the car house. The cars can be charged with 
compressed air at 2,500 pounds pressure in about two or three 
minutes' time. 

The Mannesmann bottles are all tested to a pressure of 
4,500 pounds per square inch, and as they are filled with air at 
a pressure of 2,500 pounds per square inch, there is a factor of 
safety of about 2. The question is frequently put as to the 
liability for these tubes to explode. When the tubes are filled 
with the air at 2,500 pounds per square inch there is no practi- 
cable way whereby the pressure can be increased ; in fact, the 
only thing that can happen is for the pressure to decrease. 

The recent advance made in steel structural material and 
weldless tubes has enabled the handling of pressures with abso- 
lute safety that were not heretofore thought possible. 

These high air pressures mean greater mileage of cars and 
vehicles, so that compressed-air power has taken a decidedly 
forward movement for railway and vehicle traction. 

THE COMPRESSED-AIR BOTTLE OR RESERVOIR. 

As there has been some misapprehension in regard to the 
strength of the Mannesmann air bottles or reservoirs for high- 
air pressures as used on street cars and vehicles, we submit 
some details of tests made on these tubes by the Watson-Still- 
man Company in presence of many witnesses. A Mannesmann 
steel tube 5 feet long, 8 inches diameter, and \ inch thick, 
which had been in use on a Hardie motor for about two years, 
carrying air pressure at 2,000 pounds per square inch, was used 
for the experiments. 



3io 



COMPRESSED AIR AND ITS APPLICATIONS. 



I 



The tube was first submitted to a hydraulic pressure of 
2,150 pounds, when it was struck several blows with a 14-pound 
sledge having a 3-foot handle, the sledge being swung from 
the end of the handle, and weighing, with the handle, 16 
pounds. These blows made no impression 
whatever. At 4,000 pounds the expansion was 
found to be three-thirty-seconds of an inch. 
When the pressure was removed, the bottle re- 
turned to its original measurement, this press- 
ure being near its limit of elasticity. 

A second application of pressure was then 
made up to 5,000 pounds per square inch, at 
which point the tube began to stretch, and 
between 5,000 and 6,000 pounds the tube in- 
creased one-eighth of an inch circumferen- 
tially. 

At 6, 100 pounds the bottle began to stretch 
over a small area at a point near its centre, 
and continued to do so until it was ruptured,, 
at about 6,150 pounds pressure. 

The character of the rupture was a mere 
split in the steel, 18 inches long. No pieces 
were detached and the fracture was quite 
regular in its form, showing high ductility in 
the material and freedom from any liability 
to project detached pieces in case of a rupture. 
As the tube tested had been in use in one of 
the Hardie air motors for a period of two years 
under a pressure of 2,000 pounds, this indi- 
cated that there had been no perceptible deterioration in use, and 
supported the assertion that the duration of the reservoirs may 
be considered as indefinite, and that no allowance in estimates 
of cost of operation need be made for their renewals or repairs. 
Other tests have been made of the rupture of these tubes, 
one of which, 9 inches in diameter, expanded fifteen-sixteenths 



D — AIR BOT- 
TLE. 



AIR COMPRESSORS OF THE L.-D.-G. TYPE. 3 1 I 

of an inch before fracture, showing extraordinary ductility, and 
in all the tests made in Germany and elsewhere upon these 
tubes no fragments were ever detached and the fracture was 
always of the same character, a simple longitudinal rent usually 
near the middle of the tube. 

It appears that the tubes did not begin to stretch until a 
pressure of 5,000 pounds had been reached. Consequently, 
4,000 pounds, at which all the tubes are tested, is below the 
limit of elasticity, and 2,000 pounds, which is the maximum, 
pressure under which the reservoirs are used in the Hardie: 
motors, must be considered to be absolutely safe beyond the 
possibility of rupture, and even if a rupture should occur, there 
would be no danger of flying pieces or of any serious accident.. 



COMPRESSORS OF THE LAIDLAW-DUNN-GORDON COMPANY, 
CINCINNATI, OHIO, 

Fig. 121 illustrates an outline plan and elevation of the 
duplex slide-valve compressor of this company, of the forked - 
frame type, and a process print of the same is illustrated in 
Fig. 122. Large advantages in operation are claimed for these, 
compressors from their straight-line action and the stability of 
the fork frame, which gives four bearings for a duplex com- 
pressor; the Meyer adjustable valve gear being also a leading 
feature in their steam economy. It is adjustable by hand, and 
has a range from one-fifth to four-fifths cut-off. A separate 
speed governor controls the general motion of the engine, and 
an unloading device unloads the work of the engine when ex- 
cessive pressure is reached, and provides for its continuous mo- 
tion until a fixed minimum pressure is reached in the air pipes, 
when the unloading device restores the compressor to its full 
work. The load relief prevents the compressor from stopping 
on the centre. 

The cross-compound, two-stage air compressor of this com- 
pany is detailed in outline in Fig. 123, showing the steam re- 



312 



COMPRESSED AIR AND ITS APPLICATIONS. 



ceiver and the intercooler. The Meyer adjustable cut-off is 
provided both on the high-pressure and the low-pressure cylin- 
ders. This compressor also has the straight-line action and the 




forked frame with centre crank for each engine. In Fig. 124 
is a view of this compressor in perspective. The intercooler is 
directly connected to the air cylinders, and the aftercooler is 
placed on the air cylinders at the left. This arrangement 



AIR COMPRESSORS OF THE L.-D.-G. TYPE. 



313 




3H 



COMPRESSED AIR AND ITS APPLICATIONS. 



gives dry, cool air directly to the pipe-distributing system and 
avoids all possibility of oil-vapor explosions. The company 
build about twenty sizes of single and duplex compressors for 







Fig. 123.— cross-compound, two-stage compressor. 

pressures from 35 to 3,000 pounds, and of volumes from 120 
to 3,000 cubic feet per minute. 



COMPRESSORS OF THE CLAYTON AIR COMPRESSOR WORKS, 
HAVEMEYER BUILDING, NEW YORK CITY. 

In Fig. 126 is illustrated a small post or wall compressor 
suitable for low pressures, up to 25 pounds, for operating pneu- 
matic appliances or oil burners, or for testing and inflating 
pneumatic tires, operating small sand-blasts, and spraying. 
They are also furnished with a crank handle for experimental 
use. 

In Fig 127 is illustrated a water-jacketed compressor of the 



AIR COMPRESSORS OF THE L.-D.-G. TYPE. 



315 




I 



3i6 



COMPRESSED AIR AND ITS APPLICATIONS. 







■0..: 



AIR COMPRESSORS OF THE CLAYTON TYPE. 



317 




Fig. 126.— post belt compressor. 




Fig. 127.— water-jacketed compressor. 



3i» 



COMPRESSED AIR AND ITS APPLICATIONS. 



same type as above; designed for air pressures from ioo to 250 
pounds per square inch. 

Both patterns of this compressor are made of 2\, 3, 4, 5,6, 
and 7 inches diameter, by 6 inches stroke, and will compress 




from 2 to 17 cubic feet of free air per minute up to 250 pounds 
per square inch according to their size and equipment. 

Fig. 128 shows a steam-actuated air compressor for press- 
ures up to 25 pounds with non- water-jacketed cylinder. They 
are made in sizes from 4 to 12 inches diameter of air cylinders, 
and with steam cylinders of suitable size for the required steam 



AIR COMPRESSORS OF THE CLAYTON TYPE. 



319 



and air pressure. At their rating they will compress 25 to 349 
cubic feet of free air per minute. 

In Fig. 129 is illustrated an electrically driven air compres- 
sor of the Clayton type, a most convenient method of compress- 
ing air when an electric current is available. It is made in sizes 
for small service. 

In Fig. 130 is illustrated a duplex steam-actuated compres- 
sor of the Clayton type, which is built in sizes of equal steam 
and air cylinders from 4 to 10 inches in diameter and from 5- 
to 9-inch stroke, and at rated speed will furnish from 18 to 212 




FIG. 129.— ELECTRIC-DRIVEN AIR COMPRESSOR. 



cubic feet of free air per minute ; they are water-jacketed and 
supplied with an automatic steam regulator operated by the air 
pressure. 

The air governor (Fig. 13 1) is located directly upon the 
main discharge pipe of the compressor, with a check valve in 
the main line at the flanges next to the pressure gauge in the 
figure, to prevent loss of air when the compressor is unloaded ; a 
throttle valve, operated by a weighted lever, is operated at over 
pressure by a spring-adjusted piston. The small pipe at the 
left-hand side of the figure is screwed through the air waste pipe 
and opens beneath the governor piston. Adjustment is made 



320 



COMPRESSED AIR AND ITS APPLICATIONS. 




AIR COMPRESSORS OF THE CLAYTON TYPE. 



321 



by the ball and a screw at the top of the piston cylinder which 
regulates the tension of the piston spring. It is shown in posi- 
tion in Fig. 132. 

The three-stage compressor (Fig. 133) is of the Clayton 
model, and is designed for high pressure, up to 2,000 pounds 





Fig. 131.— the air governor. 



per square inch, and is also arranged for compressing and 
liquefying carbonic acid gas. 

The steam cylinders are placed parallel, as in the regular 
pattern of duplex compressor, and the compressing cylinders 
are arranged in the same manner at the opposite end of the 
frame, and at the greatest distance from the heat of the steam 
cylinders. The air or gas enters the initial compressing cylin- 
der, and, after undergoing the first compression, passes through 
a coil surrounded by water, and thence into the second com- 
pressing cylinder, from which it is transmitted through another 



322 



COMPRESSED AIR AND ITS APPLICATIONS. 



\ 




AIR COMPRESSORS uf THE CLAYTON TYPE. 



323 



cooling coil to the third cylinder, where it undergoes the final 
compression. The coils for cooling the air or gas in transit be- 
tween cylinders are not shown in illustration. The cranks are 
arranged and the cylinders proportioned to provide for an equal 




division of load, and the compressor with its steam cylinders is 
entirely self-contained. 

The proportions of this compressor are so perfect that it 
secures maximum strength with minimum weight, together 
with a compactness and saving in floor space rarely obtained in 
a machine of its class. The fly-wheel is placed in the centre 



324 



COMPRESSED AIR AND ITS APPLICATIONS. 



avoiding all danger of injury through contact. The compress- 
ing cylinders are surrounded by water-jackets for surface cool- 
ing, and the stuffing-boxes are also cooled by a circulation of 



k 



y 



om 



mm 




i.'nMHINI l> sl'11,1. AM' AIIM'KISM Kl CUVKKXHK. 



water. The valves, both inlet and discharge, and the pistons, 
are of new design and render leakage impossible. A satisfac- 
tory method of lubrication is provided without detracting from 



AIR COMPRESSORS OF THE GUILD & GARRISON TYPE. 325 

the purity of the gas, and all the working parts are singularly 
easy of access. These are two of the most important features 
of the machine, since it is essential that all parts coming into 
contact with the gas be kept free from accumulation of impuri- 
ties of any description, and that they be open to prompt adjust- 
ment or repair. 

The Clayton combined speed and air-pressure governor 
(Fig. 134) supplies a much-needed want where both engine 
speed and air-pressure regulation are required. It is a combi- 
nation of the air governor with a speed governor, and not only 
performs the functions of the air governor already described 
by limiting the operation of the compressor to the work re- 
quired, but also prevents the compressor from operating at an 
injurious speed, should a sudden drop in the air pressure pro- 
duce a greater demand upon the compressor than its highest 
reasonable speed will supply. Thus, should the air be used to 
drive rock drills or hoists, and all of them suddenly be started 
simultaneously, the compressor, unless provided with a speed 
governor, would run at an excessively high rate of speed in 
order to supply the unusual demand. This applies in all in- 
stances where the demand for air is intermittent. This gover- 
nor is guaranteed to control both the speed of the compressor 
and the pressure of air with absolutely no attention from the 
engineer. 

AIR COMPRESSORS MADE BY GUILD & GARRISON, 
BROOKLYN, N. Y. 

Among the large variety of air compressors, air and vacuum 
pumps made by Guild & Garrison, Brooklyn, New York City, 
we illustrate the double-acting horizontal air compressor (Fig. 
135), which has found large employment in sugar refineries, 
chemical and fertilizer factories, oil works, and other industrial 
establishments for elevating acids and other liquids, blowing 
out filters and filter presses, aerating water, and for all purposes 



326 



COMPRESSED AIR AND ITS APPLICATIONS. 



flf 





AIR COMPRESSORS OF THE GUILD & GARRISON TYPE. 327 

in which dry compressed air is required. It is an excellent 
compressor for supplying air for air hammers and drills. 

In their style of tandem duplex single-acting air compressor, 
they have designed a unique form of air valve, a section of 
which is given in Fig. 136. The inlet valve in the piston has 
a split gland guide, allowing of a ready means of removing the 




-GUILD & GARRISON COMPRESSOR VALVE. 



valve for repair. The discharge valve is a radical departure 
from the older designs of compressor valves, being a flat disc 
valve covering the entire area of the cylinder and held to its 
seat by a guide and spring. Its face and the face of the piston 
are perfectly flat, so that the piston may strike the valve and 
deliver all the air with no clearance space to detract from its 
efficiency. A large area of discharge is obtained by a very 
small movement of the valve, and no pounding is made by its 
action. 



328 



COMPRESSED AIR AND ITS APPLICATIONS. 



AIR COMPRESSORS OF THE KNOWLES STEAM PUMP WORKS, 
NEW YORK CITY. 

In the following pages we illustrate the various styles of air 
compressors made by this company, with description appended 
to each illustration. 




IJKI.T WALL ok 1'OST CoMI'KKSSOK. 



Capacity, from 2 to 17 cubic feet free air per minute, and to pressures of 100 to 150 lbs. per 
square inch. Piston diameters, from 2^ to 7 inch. Stroke of all sizes, 6 inch, single-act- 
ing, without water-jackets. Largely used where a limited supply of compressed air is 
required. 



AIR COMPRESSORS OF THE KNOWLES TYPE. 



329 




Fig. 138.— vertical geared and belt air compressor. 

Triplex type with slide valves and unloading device by which the load is thrown off the 
compressor when the pressure reaches its limit in the receiver, and again put on when the 
pressure falls 2 or 3 pounds. A most convenient form for low pressures up to 15 pounds. 
Made in sizes from 480 to 3,000 cubic feet of free air per minute. 



33Q 



COMPRESSED AIR AND ITS APPLICATIONS. 



P _a £ 




E 33 



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AIR COMPRESSORS OF THE KNOWLES TYPE. 



331 




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332 



COMPRESSED AIR AND ITS APPLICATIONS. 




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AIR COMPRESSORS OF THE KNOWLES TYPE. 



333 




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334 



COMPRESSED AIR AND ITS AI PLICATIONS. 




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AIR COMPRESSORS OF THE KNOWLES TYPE. 



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Chapter XX. 



AIR COMPRESSORS— Continued 



AIR COMPRESSORS. 

{Continued.) 

AIR COMPRESSORS OF THE NORWALK IRON WORKS, 
SOUTH NORWALK, CONN. 

The entire line of compressors built by this company are of 
the compound type, in which the heat of compression is elimi- 
nated as far as possible between the two stages of compression 
by the use of intercoolers in addition to the effect produced by 
water-jacketing the cylinders. The adoption of the Corliss 
type of air valves for both inlet and exit passages of the low- 
pressure cylinders gives a full value to the capacity of this cyl- 
inder to supply the high-pressure cylinder to its full capacity at 
the discharge pressure of the low-pressure cylinder. 

By this system of compounding for the ordinary pressure 
used in rock-drilling, pneumatic tools, and the various oper- 
ations in which the required air pressure maybe from 50 to 100 
pounds, the economy in power for operating the compressor is 
very apparent, and is derived not only from the heat work 
saved by intercooling, but also from the equalizing of the cylin- 
der pressures throughout the stroke. This will be readily rec- 
ognized from the fact that the resistance to compression in the 
low-pressure cylinder is derived from a longer deliver)'- at low 
pressure in comparison with the action of a single compression 
to the full pressure. 

Again, in the high-pressure cylinder the initial pressure 
commences with the terminal pressure of the low-pressure cyl- 
inder, and its delivery pressure is also extended over a greater 
part of the stroke, thus in a large measure eliminating the 
otherwise jerky action observed in single-cylinder air com- 
pression, and thereby lessening the momentum work of the fly- 
wheel (see Table XIX. for the lost work in single- and two- 
stage air compression). 
24 



34° 



COMPRESSED AIR AND ITS APPLICATIONS. 




AIR COMPRESSORS OF THE NORWALK IRON WORKS. 341 

Under all conditions of operation of a compound compressor 
the risk of cylinder and receiver explosions, from the generation 
of oil vapor from lubricants by the heat of compression, is en- 
tirely eliminated. 

One of the great advantages derived from compound air 
compression and intercooling is found in the production of dry 
compressed air, a valuable desideratum when the compressed 
air is to be transmitted to a distance. Dry air prevents frost- 
ing in the transmission pipe in very cold weather, and the elim- 
ination of frost in the exhaust passages of drills and pumps is 
worthy of serious consideration in the choice of a compressor. 

The double compound air compressor (Fig. 145) represents 
in a sectional elevation the leading features of construction in 
the designs of this company, in which are shown : the Meyer 
adjustable cut-off on the high-pressure cylinder ; the balanced 
slide-valve on the low-pressure steam cylinder with rock-lever 
connections with the cams on the main shaft; a section of 
the Corliss valves on the low-pressure air cylinder, the inter- 
cooler also in section with the subdivisions in the intercooler 
heads ; the air surface cooling tubes expanded in the sub- 
heads of the intercooler ; the poppet valves in the high-press- 
ure cylinder and the swivel cross-head. The outside connecting 
rods and details are shown in the other illustrations. 

The use of water power is also made available through the 
operation of a turbine or Pelton wheel according to the volume 
or head of the water power. Fig. 146 represents a direct-con- 
nected Pelton-wheel compound air compressor, and Fig. 148 
represents a geared compound air compressor to be operated by 
a turbine or other water-power wheel, to which a steam cylin- 
der is attached ready for connection when water power fails. 

A three-stage air compressor, with two intercoolers, is illus- 
trated in Fig. 149. This is the standard type for charging the 
air receivers of mine locomotives. The steam end is fitted with 
adjustable steam expansion valves and speed governor. 

In operation, the air is brought from some place cool and 



142 



COMPRESSED AIR AND ITS APPLICATIONS. 




AIR COMPRESSORS OF THE NORWALK IRON WORKS. 



343 



free from dust, and is admitted to the large double-acting cyl- 
inder in the centre of the machine. Here the first stage of 
compression is performed. The water-jacket by which this 
cylinder is surrounded takes away a share of the heat of com- 




pression, after which the first intercooler extracts the remain- 
der, bringing the air to the second cylinder at or near the tem- 
perature of the cooling water. 

The second cylinder is also water-jacketed and performs 
another stage of the compression. From this cylinder the air 



344 



COMPRESSED AIR AND ITS APPLICATIONS. 




AIR COMPRESSORS OF THE NORWALK IRON WORKS. 345 

is led through the vertical pipe shown in front of the machine 
to the second intercooler, and thence into the third cylinder 
through the inclined pipe shown at the back. In this third 
cylinder, which is also jacketed, the compression is completed, 
and the air discharged at the connection shown at the bottom. 




The pistons of the second and third cylinders are in direct 
line with the piston of the first cylinder and the steam piston. 
All the strain of compression is therefore direct push and pull 
on a straight steel rod. 

This compressor has a pressure capacity of about 1,000 
pounds per square inch. 



34<5 



COMPRESSED AIR AND ITS APPLICATIONS. 



A three-stage air compressor suitable for a still higher press- 
ure is illustrated in Fig. 150. Other air compressors of this 
company are illustrated in Figs. 147, 151, 152, and 153, with 
the foregoing general features, with free-air capacities of from 



"tr 




170 to 2,350 cubic feet per minute. The sizes of the free-air 
cylinders vary from 10 to 32 inches in diameter and from 12 to 
36-inches stroke. Diameters of high -pressure cylinders about 
two-thirds the diameter of the low-pressure cylinders. 



AIR COMPRESSORS OF THE NORWALK IRON WORKS. 347 




348 



COMPRESSED AIR AND ITS APPLICATIONS. 




TIG. i52.--SMALL-SIZb.il COMPOUND A1K OK GAS COMPRESSOR. 

Steam cylinder, 6x8 inch, with compound water-jacketed cylinders, for pressures from 150 
to 500 pounds. 



A 




Fig. 153.— double compound air compressor. 

Jacketed air cylinders and intercooler, with Corliss valves on low-pressure air cylinder. 
Meyer cut-off on high-pressure steam cylinder. Balanced slide valve on low-pressure steam 
cylinder. 



AIR COMPRESSORS OF THE NORWALK IRON WORKS. 



349 



AIR PRESSURE REGULATOR. 

The regulator of the Norwalk Iron Works is illustrated in 
Fig. 154. It is placed in the line of the steam pipe near to the 
steam cylinder, the body being a perfectly balanced double- 
seated valve, controlled by the air pressure in the receiver. 
Above the regulating valve body is a small cylinder, having a 
piston connected with the bal- 
anced steam valve below by a 
stem as shown in the illustra- 
tion. Above the small piston is 
a stop screw projecting above the 
cylinder head for regulating the 
lift of the piston by the com- 
pressed air pressure beneath it. 
The air from the receiver is led 
through a small safety-valve 
shown on the left side of the cyl- 
inder in the illustration, which 
regulates the pressure at which 
the air can enter the cylinder and 

close the balanced valve. Above the disc of the small safety- 
valve is a spring whose tension to close the valve is regulated 
by a screw with a milled head, allowing the spring tension on 
the valve to be so adjusted that the valve will lift and permit 
the air from the receiver to flow under the piston, and by its lift 
close the balanced valve. The air passes into the small cylin- 
der beneath the piston, and if no escape were provided would 
drive the piston to the top of the cylinder. To regulate this 
action a very fine slot is cut in the side of the small cylinder. 
When the piston rises it uncovers this slot and thus furnishes 
an escape for the air which is passing the safety-valve. If only 
a little air passes the valve, then a small part of the slot will ac- 
commodate it and the piston will take a low position. With 
more air escaping, the piston will rise higher and uncover more 




[54.— REGULATOR. 



35Q 



COMPRESSED AIR AND ITS APPLICATIONS. 



of the slot, thus providing a larger opening for its exit. As the 
slot is very fine, a very little difference in the quantity of air will 
cause the piston to assume a high or low position. After the 
small safety-valve begins to blow, an almost insensible increase 
of pressure in the reservoir will furnish enough more air to 




Type of the Edward P. Allis Company, Milwaukee, Wis. With Corliss air valves. 



carry the piston to the top of the small cylinder. Thus any 
degree of regulation is obtained by a very little difference of 
pressure. As the air which works on the piston in the small 
cylinder has only to perform the work of lifting the piston and 
valve sufficiently to uncover enough of the slot so that it can 
escape, its pressure is very slight. The piston is fitted loosely, 



AIR COMPRESSORS OF THE E. P. ALLIS CO. 



351 




Fig. 156— compound Corliss engine-driven blowing engine. 

Vertical type for blast furnace and bessemer work. Built by the Edward P. Allis Company, 
Milwaukee, Wis. 



352 



COMPRESSED AIR AND ITS APPLICATIONS. 







-hill 







o > 



m 3 

2 A 



AIR .COMPRESSOR OF THE MERRILL TYPE. 



353 



and the whole apparatus moves as nearly without friction as 
can be imagined. 

When this regulator is applied to compressors having a sin- 
gle steam cylinder it is possible for the valve to be carried so 
high as to shut off all steam and stop the engine on the centre. 
This would be objectionable. To obviate this there is placed 
on the top of the small cylinder 
a screw stop which can be set to 
prevent the closing of the steam 
valve more than is sufficient to 
run the engine at the slowest 
speed at which it will pass the 
centre. 

The Corliss air-valve gear of 
this company is somewhat pe- 
culiar ; the valves are moved by 
cams. The shape of these cams 
is such that the valve remains 
at rest until the pressure below 
it is nearly equal to that above. 
Then the movement begins, and 
when the pressures are equal 
the valve is quickly thrown full 
open. Inclosing, the cam allows 
a rapid movement, so that the 
valve is seated before any con- 
siderable pressure comes upon 
it. The connection which draws 

it shut is elastic, so that if the valve seat is dry no cutting, .Can 
occur. This form of movement having such desirable features 
for heavy pressure is in a degree useful at any pressure, and has 
been therefore adopted for this company's standard compressors. 

The Merrill compound direct-acting air compressor (Fig. 
158) is one of the latest productions for the economical 'Com- 
pression of air for pumping water by the direct displacement 
23 




COMPOUND DIRECT-ACTING "AIR 
COMPRESSOR. 



354 COMPRESSED AIR AND ITS APPLICATIONS. 

and inductor system, and for the lesser requirement for pneu- 
matic tools. It is an improvement upon the wasteful method 
of the direct-acting air-brake pump, and claims a high efficiency 
for a vertical direct-acting type. Its action is derived from 
three steam pistons and three air pistons, each pair of steam 
and air pistons on a piston rod, and all three pairs being con- 
nected together by a cross-head, which carries a diagonal valve 
gear that shifts the ports of the steam valve by rotating a 
ported piston, which in turn throws a spool-valve linked to a 
slide-valve. There are one high-pressure and two low-pressure 
cylinders for both steam and air. Air cylinders are water- 
jacketed. The central cylinders for both steam and air are 
high pressure ; the outside are low pressure, so that each pair 
of steam and air cylinders is equalized as to strains. The 
low-pressure steam cylinders are cushioned sufficiently to pre- 
vent their pistons from striking the heads under any condi- 
tions of air compression. An intercooler is provided in the 
base of the compressor. 

AIR COMPRESSORS OF THE CURTIS & CO. MANUFACTURING 
COMPANY, ST. LOUIS, MO. 

In the following figures are illustrated the various styles of 
air compressors made by this company. They are principally 
designed for use in shops and foundries, and for the requirements 
of small operators with compressed air. In Fig. 159 is repre- 
sented the duplex single-acting belt-driven compressor, which 
is built in two sizes, 6X6 and 8X8 inches, piston and stroke. 

A section of the working parts is shown in Fig. 160, and the 
valve seat and valve cap in Figs. 161 to 164. The working 
parts are entirely enclosed in order to exclude the dust of a 
shop from the valves and cylinders. The trunk pistons are 
packed with metallic rings, and the cylinders and heads water- 
jacketed. 

In Fig. 165 is represented the duplex single-acting com- 
pressor with a vertical steam engine all mounted on a single 



AIR COMPRESSORS OF THE CURTIS & CO. TYPE. 



355 



base. In this arrangement the engine crank is set at right 
angles with the compressor cranks, so that the greatest resist- 
ance during compression receives the highest pressure in the 
steam cylinder. 

The working parts of this compressor are shown in section 
on preceding page. 

In Fig. 166 is shown a sectional elevation from the drawing 




Fig. 159.— duplex vertical air compressor. 
Belt driven. 



of the belt-driven compound or two-stage compressor of the 
Curtis Company, the cylinders of which are 13 and 8 inches 
diameter by 12-inch stroke, with an intercooler shown in the 
vertical section on the next page. 

The general construction and valves are the same as in 
other compressors of this company. Capacity at 120 revolutions 
is 100 cubic feet of free air per minute at 100 pounds pressure. 



356 



COMPRESSED AIR AND ITS APPLICATIONS. 




Fig. 160.— section. 



AIR COMPRESSORS OF THE CURTIS & CO. TYPE. 



357 



A larger size on the same plan has a capacity of 200 cubic feet 
per minute. 

In Fig. 167 is a sectional end elevation of the smaller cylin- 
der showing the air inlet from the intercooler, valve location, 





Fig. 161.— valve. Fig. 162.— valve. 

and air discharge, figured on the same scale as the front section 
on previous page. 

These compressors are provided with both an air-pressure 
and speed governor. The air-pressure governor automatically 
stops the compression of air without stopping the machine. 

The gas and gasoline engine compressor of this company 
(Fig. 168) is a most compact arrangement suited for supplying 
compressed air for hammers and riveters in construction work. 





" 



Fig. 163.— seat. 



Fig. 164.— cap. 



The air cylinders are single-acting and connected by gearing to 
the gas or gasoline engine so that the engine makes two revo- 
lutions to one of the compressor. The cranks are so arranged 
that the motor stroke of the engine corresponds with the com- 
pressing stroke of the compressor. Cylinders of engine and 
compressor are water-jacketed. They are built for free-air 
capacity from 25 to 200 cubic feet per minute. 



358 



COMPRESSED AIR AND ITS APPLICATIONS. 




Fig. 165.— steam driven duplex compressor. 
Mounted on common base. 



AIR COMPRESSORS OF THE CURTIS & CO. TYPE. 



359 




Fig. 166— section of belt-driven compound air compressor. 



360 



COMPRESSED AIR AND ITS APPLICATIONS. 




Fig. 167.— end sectional elevation of compound air compressor. 
Showing location of intercooler. 



AIR COMPRESSORS OF THE N. Y. AIR COMPRESSOR CO. 



361 




FIG. 16S.-THE GAS-ENGINE AIR COMPRESSOR. 



AIR COMPRESSORS OF THE NEW YORK AIR COMPRESSOR 
COMPANY. 

The compressors of this company have been designed espe- 
cially for supplying compressed air for the operation of pneu- 
matic hammers, drills, riveters, hoists, and other tools used in 
shop and construction work, although equally applicable to 
driving rock drills, coal-cutters, and other mining machinery, 
pumping water by the air-lift system, operating signals, clean- 
ing cars and cushions, elevating acids, and other uses of com- 
pressed air. 

The Corliss type of compressor shown in Fig. 169 is em- 
ployed in installations of large capacity, and is built with 



362 



COMPRESSED AIR AND ITS APPLICATIONS. 



duplex or compound steam or air cylinders, either condensing 
or non-condensing. 

The compressor shown in Fig. 170 has duplex steam cylin- 
ders with Meyer adjustable cut-off, and compound air cylinders 




Fig. 169. -the corliss type. 

with intercooler. This compressor is built in four sizes, rang- 
ing in capacity from 500 to 2,000 cubic feet of free air per min- 
ute, and when the available steam pressure is sufficiently high 
the steam cylinders are compounded also. The intercooler 
consists of a set of composition metal tubes encircled by a steel 






shell, the cooling water passing through the tubes and the air 
circulating around them. 

The duplex steam-driven air compressor of this company is 
illustrated in Fig. 171. It has cylinders and heads water- 
jacketed, and is provided with both speed and pressure control- 



AIR COMPRESSORS OF THE N. Y. AIR COMPRESSOR CO. 363 

lers. The large sizes are built with the Meyer adjustable cut- 
off, a most substantial and efficient compressor for any work. 







/'j&Qk 


m 1 1 










? , 






syif " 




— , ■■■— ''■ i 


HmT "*""— .jj 




—i 




1 .. 


f 



Fig. 171.— duplex type with governor. 

They are made in sizes of 7 X 7-inch air cylinders with equal- 
sized steam cylinders, and in five sizes up to 16 X 18-inch air 
cylinders with equal-sized steam cylinders, and of capacity from 
80 to 1,000 cubic feet of free air per minute. 

Fig. 1 72 represents a single straight-line steam-driven air 
compressor, also built by the same company. This type is ad- 




FlG. 172.— STRAIGHT-LINE COMPRESSOR. 



vantageous for field work and for other classes of service pre- 
senting conditions rendering the single style of compressor 
preferable to the duplex. 



364 



COMPRESSED AIR AND ITS APPLICATIONS. 



Fig. 173 illustrates a horizontal, duplex, belt-driven air com- 
pressor with air-pressure controller that unloads the work of the 
compressor whenever an over-pressure is attained by the 







Fig. 173.— duplex belt compressor. 

stoppage of work on air tools. They are made in air-cylinder 
sizes from 7 X 7 to 16 x 18 inches, and of capacity from 80 to 
1,000 cubic feet of free air per minute. 

The single style of belt-driven air compressor shown in Fig. 
174 is adapted to the same service as the duplex machine last 




-SINGLE BELT COMPRESSOR. 



described, and is sometimes preferred because of the more lim- 
ited floor space occupied by it. This compressor is built in 
sizes ranging from 100 to 500 cubic feet of free air per minute, 



AIR COMPRESSORS OF THE N. Y. AIR COMPRESSOR CO. 365 

and is provided with automatic unloading device for controlling 
its operation to suit the demand made upon it. 

The vertical air compressor, belt-driven (Fig. 175), is pro- 




FlG. 175.— THE VERTICAL AIR COMPRESSOR. 



vided with water-jacketed cylinders and heads ; a substantial 
machine, with poppet valves, and suitable for any pressure 
used in shop and constructive work. 



Chapter XXI. 



AIR COMPRESSORS— Continued 



AIR COMPRESSORS. 

{Continued.) 

AIR COMPRESSORS OF THE RAND DRILL COMPANY, 
NEW YORK CITY. 

Figs. 176 and 177 show the standard forms of the air cylin- 
ders of this company, which are water- jacketed, and in some of 
the designs the heads are also water-jacketed. Valves are of 
the poppet type. 

The unloading device by the opening of a valve from exces- 
sive pressure allows the air on the compression side of the pis- 




FlG. 176.— AIR CYLINDER WITH HOODED HEADS AND POPPET VALVES. 

ton to pass over to the inlet side and thus relieve the piston of 
its load until the receiver pressure falls below the working 
pressure, when the weight closes the valve and the compressor 
resumes its work. 

The air-valve gear of this company is a novelty in valve con- 
trol. Experience has shown that the ordinary poppet valves 



370 COMPRESSED AIR AND ITS APPLICATIONS. 

as usually held under a spring are liable to chatter more or less, 
and that by making the springs stronger to reduce the chatter- 
ing the lift of the valves is also reduced, which restricts admis- 
sion, and therefore a larger number of inlet valves are required 
or the efficiency of the compressor is lessened. 

The mechanical poppet-valve gear shown at Fig. 179 has a 
yoke frame at each end of the cylinder connected by outside 
rods. To the yoke frames the inlet and outlet valves are con- 




FlG. 177.— THE UNLOADING DEVICE FOR A BELT COMPRESSOR. 

nected, not rigidly, but with spring tension, so that all the 
valves have a positive movement at the proper moment to a 
wide-open or closed position, the springs operating to soften 
the impact of the valves. The valve gear is operated from an 
eccentric on the main shaft. 

The valves thus operated have their equivalent area largely 
augmented, and thus require a less number of valves to a cylin- 
der than when fitted with the ordinary poppet valve with 
springs only. 

In Fig. 181 is illustrated the complete cross compound Corliss 
air compressor of the Rand Drill Company, in which the low- 
pressure cylinder is provided with the Corliss inlet valve, the 



AIR COMPRESSORS OF THE RAND DRILL COMPANY. 37 1 







372 COMPRESSED AIR AND ITS APPLICATIONS. 




Fig. 179.— the hand air valve gear. 




Fig. 180.— the CORLISS inlet valve ; poppet discharge valves. 



AIR COMPRESSORS OF THE RAND DRILL COMPANY. 



373 




374 COMPRESSED AIR AND ITS APPLICATIONS. 

discharge and high-pressure valves being of the free poppet 
type. The box-like connection between the cylinders contains 
the intercooling pipe coil as shown in the section on intercooling. 
Fig. 183 represents the cross compound steam and air cylin- 
der type of this company, with removable water jackets on the 
air cylinders — a valuable consideration for the efficiency of an 



- -- j g P^a ,|H|, H ||, 

4 £' 






J 




FIG. 182. -AIR CYLINDER ; CORLISS INLET AND DISCHARGE VALVES. 

air compressor where limy or muddy water must be used for 
cooling cylinders and intercooler. 

In the various sizes and combinations of the compressors of 
the Rand Drill Company, numbering about twenty, the capaci- 
ties vary gradually from 350 to 6,000 cubic feet of free air per 
minute. The compound or two-stage compressors are intended 
for final pressures up to 100 pounds pressure per square inch. 
In the low-pressure cylinder, compression takes place from 
atmospheric pressure to 27 pounds, delivering to the inter- 



AIR COMPRESSORS OF THE RAND DRILL COMPANY. 



375 




Fig. 183.— cross compound steam and air cylinders 
With removable water jackets and intercooler. 




J 







Pig. 184.— the imperial type air compressor. 



376 



COMPRESSED AIR AND ITS APPLICATIONS. 



cooler at about 240 F. and to the high-pressure cylinder at 
normal temperature. When the full pressure of 100 pounds is 
obtained the air is delivered at a temperature of 240 F., or in 
the like proportion for other required working- pressures, vary- 
ing from 50 to 1 10 pounds per square inch. 

A new design of self-contained duplex or compound air com- 
pressor has been brought out by the Rand Drill Company (Fig. 
184), in which the steam and air piston rods are connected 
by a yoke within which the crank and connecting-rod are 

contained. Cranks at right 
angles, with heavy central fly- 
wheel, and all cylinders over- 
hung. Inlet valves of Corliss 
type driven from eccentrics on 
shaft with poppet discharge 
valves. The bath system of 
lubrication is provided for the 
main bearings, crank pins, 
crosshead slides, and eccentric 
straps, the oil being distrib- 
uted by the dip of the crank 
discs. 

This type of compressor is 
made in six sizes with capaci- 
ties from 140 to 1 ,000 cubic feet 
of free air per minute. The 
fly-wheel has a broad face, crowned to receive a driving belt, so 
that the compressor may be driven by other machinery, or may 
drive other machinery if required. 

The Imperial belt compressor of this company (Fig. 185) is 
of the vertical type with single-acting trunk pistons connected 
to cranks set opposite to each other. The belt pulley is very 
large and heavy with broad face to give ample power direct from 
the belt. For pressures above 2 5 pounds the cylinders are water- 
jacketed. Inlet and outlet valves are of the poppet type. The 




Fig. 185.— imperial belt compressor. 



AIR COMPRESSORS OF THE RAND DRILL COMPANY. 377 

inlet valves of both cylinders have a common passage which can 
be connected to an air pipe from outdoors for cool air free from 
dust. It is designed as a special air compressor for shop tools, 
hammers, chisels, riveters, etc., and has an unloading device that 
stops the compression of air without stopping the machine, 




Fig. 186.— high-pressure compressor. 

when the pressure reaches its limit. It is made in seven sizes 
of capacity, from 11 to 275 cubic feet of free air per minute. 

STEAM-ACTUATED HIGH-PRESSURE COMPRESSORS. 



In Fig. 186 is illustrated the small vertical two-stage com- 
pressor with box water jacket for high pressures. In these 
compressors the entire air cylinders and connecting-pipes are 
covered with a large body of water, which insures a thorough 
cooling of the air or gas throughout the operation of compres- 
sion. They are in use for the production of liquid carbonic 
acid gas, and work up to a thousand or more pounds per square 
inch. 



378 COMPRESSED AIR AND ITS APPLICATIONS. 





Fig. 187.— high-pressure compound compressor. 




%$¥&,& 



■' 



Id 



Fig. 188. -three-stage compressor. 



AIR COMPRESSORS OF THE RAND DRILL COMPANY. 



379 



Fig. 187 represents the same style of compound compressor 
with jacketed cylinders and intercooler; front and side view. 

In Fig. 188 is represented the three-stage, high-pressure, 
steam-actuated compressor of the Rand Drill Company for com- 
pressing air to very high pressures, 2 , 500 pounds or more. This 
type of compressor is much used for liquefying carbonic acid 




-FOUR-STAGE 



gas and for compressing oxygen, hydrogen, and other gases for 
experimental work and for transportation in steel bottles. 

Fig. 189 represents the four-stage air and gas compressor. 

In Figs. 190 and 191 are illustrated the direct-acting air 
compressors of the Marsh type, built by the American Steam 
Pump Company. A model type of portable and light construc- 
tion, suitable for operating pneumatic tools. 

Fig. 192 represents the duplex vertical air compressor of 
the St. Louis Steam Engine Company. 



3 8o 



COMPRESSED AIR AND ITS APPLICATIONS. 




Fig. igo.— air compressor, American steam pump company, battle creek, mich. 
Direct acting. 




Fig. 191.— air compressor, American steam pump company. 
Direct acting. Smallest size, 2^ X 2-inch air cylinder. 



AIR COMPRESSORS OF THE ST. LOUIS S. E. COMPANY. 38: 




Pig. 192.— vertical duplex air compressor. 

Supplying from 50 to 120 



St. Louis Steam Engine Co. Three sizes built — 6 x 6, 7 x 7, 8 > 
cubic feet of free air per minute. 



38: 



COMPRESSED AIR AND ITS APPLICATIONS. 



AIR COMPRESSORS AND BLOWING ENGINES OF THE PHILADEL- 
PHIA ENGINEERING WORKS, LTD. 

This company's air compressors and blowing engines for 
blast furnaces are fitted with the Corliss steam and Gordon air- 
valve gear. In Fig. 193 is shown the operation of the posi- 
tive valve system in these compressors. The inlet valves are 
opened and closed by an eccentric operating directly through 




PIG. 193. —THE CORLISS AIR COMPRESSOR CYLINDER. 

With Gordon valve movement. 



the wrist plate. The outlet valves are operated by the same 
wrist. 

The outlet valves are opened when the pressure within the 
cylinder reaches that of the discharge, and are closed from the 
action of the same wrist plate that operates a spool piston in 
an auxiliary cylinder for each discharge valve, one end of which 
is larger than the other. The larger end is in constant con- 
nection with the compression cylinder and the smaller end with 



AIR COMPRESSORS OF THE D'AURIA TYPE. 383 

the discharge chamber, the office of which is to relieve the fric- 
tion on the Corliss valve and throw it wide open at the moment 
that the pressures in the cylinder and discharge chamber are 
equal. 

A HYDRAULIC-CONTROLLED DIRECT- ACTING AIR COMPRESSOR. 

In Fig. 194 is represented a new departure in the construc- 
tion of direct-acting air compressors. 

The D'Auria air compressor is a non-rotative compressor of 
the duplex type. So far as steam economy is concerned, it may 



. :- 








- ■ 





FIG. 194.— D'AURIA NON-ROTATIVE AIR COMPRESSOR. 

be said to have less limitations than even a crank and fly-wheel 
compressor, for the simple reason that, while in the latter the 
high degree of steam expansion calls for heavier fly-wheels, 
heavier crank shafts, etc., the moving parts of the D'Auria 
compressor are not in the least affected by the degree of steam 
expansion, and the machine works equally well with a high or 
with a low expansion. 

Since there is no mechanism of fly-wheels, connecting-rods, 
and crossheads employed to equalize the propelling force and 
the resistance at every point of the stroke, the question arises, 



3§4 



COMPRESSED AIR AND ITS APPLICATIONS. 



How is perfectly smooth action attained in the D'Auria com- 
pressor, starting the stroke with a high initial pressure of steam 
against no resistance, and ending the stroke with a propelling 
force practically nil and with resistance at a maximum ? 

This result is accomplished by a "hydraulic compensator," 
which is a cylinder, A A, Fig. 195, fitted with a plunger, B, 
carried by the same piston rod which connects the steam and 
the air piston. The ends of the compensator cylinder commu- 
nicate with each other by means of a loop of pipe, C C C, turned 




Fig. 195— section d'auria air compressor. 



into the form of a very rigid bed-plate, which adds to the 
strength of the machine and preserves, under all conditions, 
the alignment of the piston rod. This cylinder and pipe are 
filled with water or any other liquid ; and as there is no loss 
of liquid be3^ond that which may leak through the stuffing- 
boxes, they are easily kept full from any source of water 
supply, through the small pipe and two check valves, shown 
in Fig. 195. 

When the compressor is in action, the liquid column con- 
tained in the compensator pipe is affected reciprocally, to and 
fro, by the plunger, and acts in exactly the same manner as a 
balance wheel in a watch, taking up the excess of energy in the 
first half, and giving it back in the second half of the stroke 
with an exceedingly small loss due to friction. 

These compressors have no dead centres. The cycle of their 
action being limited to the period of one stroke, they are able to 



AIR COMPRESSORS OF THE ELECTRIC TYPE. 



335 



start and stop instantly, and, if fitted with a sensitive pressure 
regulator, will stop completely on a small variation of air press- 
sure, and will start promptly when that pressure falls slightly 
below the normal. They are also built with compound steam 
and air cylinders. 

These compressors are the invention of Mr. Luigi d'Auria, 
of Philadelphia, and are manufactured by the D'Auria Pumping 
Engine Company, Drexel Building, Philadelphia, Pa. 




.-"■ ■: ■■■ 



Fig. 196.— the electric-driven air compr 

Vertical type, directly geared to an electric motor. Built in seven sizes, single, of free-air 
capacity from 5 to 170 cubic feet per minute. 



386 COMPRESSED AIR AND ITS APPLICATIONS. 

AIR COMPRESSORS OF THE STILLWELL-BIERCE & SMITH-VAILE 
COMPANY, DAYTON, OHIO. 

These air compressors are built in several combinations and 
of a large number of sizes, from 20 to 1,400 cubic feet of free 
air per minute. 









# 



■ ;■•■ - 



M 



AIR COMPRESSORS OF THE S.-B. & S.-V. COMPANY. 



387 




W-, 




3 88 



COMPRESSED AIR AND ITS APPLICATIONS. 




o, si 






- X . 1>. 









AIR COMPRESSORS OF THE S.-B. & S.-V. 



COMPANY. 



389 






v_ 



Va^&S^ 






390 COMPRESSED AIR AND ITS APPLICATIONS. 







^H 


Hhv & 








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Mm 




if* 








/' 1 ' 


~7it 


^air'K^''' n ''™^°^*^%^^^i /"^SS' <5 






. M "' i ' 




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fflBB^r'"-- 




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Fig. 2oi.— the fisher aik compressor. 





Fig. 202.— lever air pump. 



Fig. 203.— post lever air pump. 



AIR COMPRESSORS OF THE SEDGWICK-FISHER COMPANY. 391 

In Fig. 201 we illustrate the Fisher air compressor made by 
the Sedgwick-Fisher Company, Chicago, 111. Its principal 
novelty is the facility of its attachment to any engine by ex- 
tending the engine piston rod through the back head and con- 
necting it to the piston rod of the compressor, the air cylinder 
being connected by stay rods to the back head of the engine. 
This seems to be a most economical method of installing a com- 
pressed-air plant in shops and mills where the engine is not 
doing full duty. The plant as illustrated is in operation in S. 
Freeman & Sons' Works at Racine, Wis. 

Apart from the bicycle air pump for its special work, there 
is no small air compressor so convenient for quick service as 
the table pump (Fig. 202), and the post pump (Fig. 203). The 
first can be screwed to a table or bench, and the second can be 
screwed to a post, for any service under 150 pounds pressure 
per square inch. They are furnished by the Gleason-Peters 
Air Pump Company, New York City. 

The action of the lever is such that the leverage increases 
with the increase of pressure by compression, a most desirable 
requisite in a hand-operated air pump. • The air capacity is 
about 36 cubic inches of free air per stroke. 

■ AIR COMPRESSORS OF THE NORDBERG MANUFACTURING 
COMPANY, MILWAUKEE, WIS. 

We illustrate in Fig. 204, and following, the air compressors 
of the above company and the leading features of their design. 
The valve gear consists of a triple wrist arm running on a 
strong trunnion bolted to the cylinder, an eccentric on crank 
shaft connected to the wrist arm by an intermediate carrier arm. 
The connecting rods between the wrist arm and the valve arms 
are arranged for a quick and full opening and closing of the 
inlet valves, while the setting of the valves is made by adjust- 
ing screws on the hub of the valve arms. 

In Fig. 205 is shown the unloading device, which is a re- 



392 



COMPRESSED AIR AND ITS APPLICATIONS. 



leasing mechanism which permits the regular operation of the 
inlet valves so long as the air pressure does not exceed the 
normal. When this pressure is exceeded the trip on the suc- 
tion valves is released and the valve left wide open, relieving 
the compressor of its load. This is effected by a loaded plunger 




subject to the air pressure which acts upon a set of knock- off 
cams, in action similar to the release hook of the Corliss gear. 

The combined pressure and speed regulator of this company 
(Fig. 208) consists of a frictionless plunger loaded with a spring 
and weight, and a centrifugal governor. These two mechanisms 
are connected to a floating lever in such a manner that they 



AIR COMPRESSORS OF THE NORDBERG MFG. COMPANY. 393 

can act independently of each other on the expansion gear of 
the engine, the adjusting rod of which is also connected to the 
floating lever. The centrifugal governor is extremely static, 
to such a degree that the speed required to lift it to its highest 
position is four times that necessary to just raise it clear of the 



© 



Ji 



r 



m m 





i 




5. — THE UNLOADING DEVICE. 



sustaining collar. The plunger is actuated by the air pressure, 
which is counteracted principally by the weight, while the 
spring pressure is only sufficient to produce a slightly increas- 
ing resistance as the plunger is depressed. The connection 
between the two elements of regulation and the expansion gear 



394 COMPRESSED AIR AND ITS APPLICATIONS. 



I 






t 



; 




■i > 



< 



r'- 



" >) 



V « 



''v-j. 




AIR COMPRESSORS OF THE NORDBERG MFG. COMPANY. 



395 



is such that a rise of the governor (or increase of engine speed) 
and an increase of air pressure produce the same effect, viz., 
a shorter cut-off. In a well-designed compressor the mean 
effective air pressure, and consequently the mean effective steam 




pressure, is practically the same at all speeds, and the point 
of cut-off is therefore fixed and independent of the speed. 
Bearing in mind this fact, the action of the governor will be 
readily understood. When the pressure tends to drop, due to 



39 6 



COMPRESSED AIR AND ITS APPLICATIONS. 



an increased consumption of air, the plunger is forced higher 
up into its barrel by the action of the spring and the engine is 
momentarily given more steam, which causes it to accelerate 







Fig. 208.— combined pressure and speed regulator. 



its motion. The acceleration causes the governor to rise, and 
thereby shorten the cut-off, until it reaches such a height that 
it brings the cut-off gear back to about its original position, 
when the speed of the compressor will settle down to that cor- 



AIR COMPRESSORS OF THE NORDBERG MFG. COMPANY. 397 

responding to the new position of the governor. The reverse 
action takes place when the air pressure tends to rise. A per- 
fectly constant air pressure can thus be maintained under all 
variations of the rate of consumption of air. 

Other compressors of the Nordberg Company are illustrated 
in Figs. 209 to 214 and an intercooler in Fig. 215. 



*£?* 




398 



COMPRESSED AIR AND ITS APPLICATIONS. 




AIR COMPRESSORS OF THE NORDBERG MFG. COMPANY. 399 




4QO 



COMPRESSED AIR AND ITS APPLICATIONS. 




AIR COMPRESSORS OF THE NORDBERG MFG. COMPANY 



401 




402 



COMPRESSED AIR AND ITS APPLICATIONS. 








AIR COMPRESSORS OF THE NORDBERG MFG. COMPANY. 403 




404 



COMPRESSED AIR AND ITS APPLICATIONS. 



THE GAS AND GASOLINE ENGINE IN AIR COMPRESSION. 

The field of usefulness of compressed air is already large, 
and is continually broadened by the increasing facilities for its 
production by simple means that may be easily transported to any 




needed location. This has been found in the adaptation of the 
gasoline engine for power and its combination with an air com- 
pressor. There is probably nothing so economical, within its 
limits of power, for compressing air as the gasoline engine ; and 
certainly no means so easily transported to any required loca- 



AIR COMPRESSORS OF THE GASOLINE TYPE. 



405 



tion for temporary work. In the vast output of modern steel 
construction of buildings and bridge-work, compressed air now 
performs a vital portion of the work of assembling such struc- 
tures, and has found its great aid in the portable air compressor 




^ 



as a reliable power producer for operating air drills, hammers 
for riveting and chipping, and air lifts. 

In Fig. 216 is illustrated the single-acting air compressor 
of the Fairbanks-Morse Company, with engine and air cylin- 
ders arranged in line and the pistons connected by a yoke and 



406 



COMPRESSED AIR AND ITS APPLICATIONS. 



rods. The engine is of the four-cycle type, with two fly-wheels 
heavy enough to carry the air piston over a second stroke. 

Figs. 217 and 218 show the cross-connected double- 
acting air compressor and gasoline engine. The massive 




frames of engine and compressor are strongly bolted together 
so as to make three rigid bearings for the crank shaft, which 
has a centre crank for the engine and an outboard crank for the 
compressor. The air valves are of the removable cage type 



AIR COMPRESSORS OF THE KEROSENE-OIL TYPE. 



407 



with seating springs. The engines are provided with electric 
and tube igniters, and a self-starting device with pump and 
gasoline charger, which is a most essential feature in a gaso- 
line engine having a fixed load. 



A KEROSENE-OIL COMPRESSOR. 



The lines of economy are rapidly advancing in the devices 
for compressing air, and kerosene as a power fuel has come to 




ID 



Fig. 219.— kerosene-oil-actuated air compressor. 

the front in the Merrill oil-actuated air compressor (Fig. 219), 
which is a self-contained and portable power, suited for all 
places in which a cheap and movable power is requisite, and 
well adapted for the operation of pneumatic tools on structural 
and bridge work. For the production of air power for oper- 



408 COMPRESSED AIR AND ITS APPLICATIONS. 

ating pneumatic pumping systems it is the cheapest and most 
convenient power in use, save some special conditions of water 
power. These air pumps operating with kerosene oil use less 
than one pint of oil per horse power per hour. The oil is 
stored in the base of the engine, is supplied to the vaporizer by 
a small pump, and is vaporized by the heat of the exhaust. A 
blow lamp is used for starting the vaporizer. 

COMBUSTION AND EXPLOSIONS IN COMPRESSOR CYLINDERS, 
RECEIVERS, AND PIPE LINES. 

Ignition in compressor cylinders, receivers, and air pipes 
has been an occasional theme of discussion among engineers 
and operators of compressed-air plants, with sometimes misgiv- 
ings in regard to its dangerous conditions. The danger has 
been over-rated, as it is well known that the explosive power of 
hydrocarbon vapor and air mixtures, even under the compres- 
sion pressures, of gas and oil-vapor engines seldom exceeds 300 
pounds per square inch. Such being the case, most air receiv- 
ers have a limit of strength equal to this or more, so that as a 
precaution receivers that are used for pressures of any amount 
should have a tensile tested strength of at least five times the 
working pressure, and six times may be considered a safe test. 
As to the conditions of safety and danger, the following re- 
marks from that valued journal, Compressed Air, are pertinent 
to the question in all its bearings: 

" Compressed air claims to be and is a safe power. Occa- 
sionally we hear of a case of firing, which to some may appear 
to be a serious objection to the use of air; but if the causes are 
known and understood and due care is observed, firing becomes 
merely a matter of carelessness. . . . Compressed air is not 
inflammable, but during compression by mechanical means it is 
found advisable to use oil, and this oil, or the gases from it, are 
the sources of combustion. In most cases firing may be traced 
to the use of poor oil, but in others too much oil sometimes 



COMBUSTION AND EXPLOSIONS. 4O9 

causes ignition. It is a common mistake of engineers in charge 
of compressors to feed oil too rapidly to the air cylinder. It is 
simply necessary to supply oil enough to keep the interior of 
the cylinder and the moving parts moistened. Where steam is 
used there is a tendency to cut away the oil, hence engineers 
grow accustomed to feeding a larger supply than is required in 
an air cylinder. There is nothing to cut or absorb the oil in 
the air end ; in fact, it is only after a considerable lapse of time 
that oil can get away when fed into the cylinder. There is no 
washing tendency as with steam, and a drop now and then is 
all that is required to keep the parts lubricated. Where too 
much oil is used there is a gradual accumulation of carbon, 
which interferes with the free movement of the valves and 
which chokes the passages, so that a high temperature may for 
a moment be formed and ignition follow. It is well to get the 
best oil, and to use but little of it. 

" There are cases where firing has arisen from the introduc- 
tion of kerosene or naphtha into the air cylinder for the purpose 
of cleaning the valves and cutting away the carbon deposits. 
Every engineer knows how easily he may clean his hands by 
washing them in kerosene ; and as this oil is usually available, 
we have seen men introduce it into the air cylinder through a 
squirt-can at the inlet valve. This is a very effective way of 
cleaning valves and pipes, but it is a source of danger, and 
should be absolutely forbidden. High-grade lubricating oils 
are carefully freed of all traces of benzine, naphtha, kerosene, 
and other light and volatile distillates. The inflammability of 
the latter is so acute that it is a dangerous experiment to intro- 
duce anything of this kind into an air cylinder; and if any of 
our readers have had an explosion in a case where the engineer 
uses kerosene, it may be traced to this source. Closed inlet 
passages leading to the air cylinder through which the free air 
is drawn from outside the building have many advantages, but 
one seldom thought of is that they interfere with the tendency 
of the engineer to squirt kerosene into the cylinder. 



410 COMPRESSED AIR AND ITS APPLICATIONS. 

" Soft-soap and water is the best cleanser for the air cylin- 
der, and it is recommended even in cases where the best oil is 
used. Long service will result in more or less accumulation of 
carbon ; hence it is advised that engineers, once or twice a 
week or oftener if necessary, fill the oil cup with soft-soap and 
water and feed it into the cylinder as the oil is fed. 

" Ignition in compressed-air discharge pipes and passages is 
not uncommon. At times this ignition is in the nature of an 
explosion. Two air receivers were blown up during the con- 
struction of the New York Aqueduct ; in one case the engine 
room was destroyed by fire resulting from this explosion. We 
have also records of two other cases where spontaneous explo- 
sions in the air receiver have resulted in the destruction of the 
engine room by fire. Other instances occur where ignition 
takes place near the air compressor, the pipes becoming red- 
hot at the joints. This ignition has been known to extend into 
the air receiver, and in one instance the flames were carried 
down into the mine by the compressed air. 

" In all such cases large volumes of compressed air were 
used. It is plain that the cause of the explosion or ignition is 
an increase of temperature above the flash point of the oil 
which is used to lubricate the compressor. A thick or cheap 
grade of cylinder oil should never be used in an air compressor. 
Thin oil which has a high flash point, and which is as free from 
carbon as conditions of lubrication will admit, is the best oil. 
A correspondent calls attention to explosions where the flash 
point of the oil is 554 F., and ignition point 606 F. We 
know of an instance where ignition took place with oil which 
had a flash point of 5 7 5 ° F., ignition point 625 F. Conditions 
were similar to those mentioned by our correspondent, that is, 
the air was compressed to about 60 pounds per square inch 
gauge pressure. If the temperature of the air before admission 
to the compressor is 6o° F., and it is compressed to 58.8 
pounds gauge pressure, the final temperature, where no cooling 
is used during compression, will be 369. 4 F., or a total increase 



COMBUSTION AND EXPLOSIONS. 411 

of 309. 4 . If air is admitted at 6o° F., is compressed without 
cooling to 73.5 pounds gauge pressure, the final temperature 
will be 414. 5 F., and the total increase of temperature 354. 5 . 
Under such circumstances the question naturally arises, How is 
it possible when using oil with an ignition point of over 6oo° 
to get an ignition, especially as water jackets and other methods 
of cooling are used which should reduce the final temperature ?. 
The figures are also based on dry air, which increases in tem- 
perature during compression to a greater degree than moist air, 
and it is known that air that is used in compressors is never 
very dry. The theoretical figures show that in order to get 
ignition with the oil mentioned, the gauge pressure should be 
about 200 pounds per square inch, where no cooling takes place. 
" It is plain that there must be an increase of temperature 
or ignition would not take place. This increase of temperature 
may result either from an increase of pressure which is not 
recorded on the gauge, or there may be an increase of temper- 
ature without a corresponding increase of pressure. Take the 
first instance, and it is not difficult to understand that an air 
compressor might deposit carbon from the oil in the discharge 
passages or discharge pipes which in the course of time will 
accumulate and constrict the passages so that they do not freely 
pass the volume of air delivered by the compressor, hence a 
momentary increase of pressure might exist in the cylinder 
heads or in the discharge pipe which leads from the air cylin- 
der to the receiver; this momentary increase of pressure would 
surely carry with it an increase of temperature which might 
exceed the ignition point of the oil. A badly designed com- 
pressor with inefficient discharge passages might produce this 
trouble. Too small a discharge pipe or too many angles in dis- 
charge pipes might also tend to produce explosions. But we 
have known instances where ignition has occurred in a well- 
designed system, hence we must look for other causes. In our 
judgment the majority of cases may be traced to an increase 
of temperature without an increase of pressure ; this increase of 



412 COMPRESSED AIR AND ITS APPLICATIONS. 

temperature can be excessive only when the temperature of 
the incoming air is excessive. A hot engine-room from which 
air is drawn into the cylinder is a bad condition. We have 
known cases where the incoming air was drawn from the neigh- 
borhood of the boiler, the temperature being close to 150 F. 
This means, of course, that if the total increase of temperature 
when air is compressed to 73.5 pounds gauge pressure is 354. 5 , 
the temperature of the initial air should be added to this figure, 
and that the final temperature might be 504. 5 . 

" But we have known ignition to take place when the tem- 
perature of the incoming air was normal, when the discharge 
passages and pipes were free and of ample area, hence we must 
look for some other cause. The only possible explanation is 
that the temperature of the incoming air is made excessive by 
the sticking of one or more of the discharge valves, thus letting 
some of the hot compressed air back into the cylinder to influ- 
ence the temperature before compression. When a piston of 
an air compressor has forced a cylinder volume of air through 
the discharge valve, and when this piston has its direction of 
movement reversed, there will immediately be a tendency of the 
air just compressed and discharged to return to the cylinder. 
In this it is checked by the discharge valve, but through long 
and constant use these discharge valves become encrusted with 
carbon and are not free to move, hence there may be a moment 
when one of these valves sticks, or it may not seat properly ; in 
either case there will be some hot compressed air in the cylin- 
der when the piston starts on its return stroke of compression ; 
the air may have lost its pressure, but not its temperature, and 
it is not difficult to understand a leaky discharge valve letting 
enough air back into the cylinder to increase the initial tem- 
perature to two or three hundred degrees. If so, and we are 
compressing air to 73.5 pounds gauge pressure, we have say 
300 temperature in the free air before compression, and as 
the increase is 3 54. 5 , the resulting temperature might be 
654.5°- 



COMBUSTION AND EXPLOSIONS. 413 

" As a remedy we would suggest more care in selecting the 
best air compressor and in frequent cleaning of the discharge 
valves and passages. The best air compressors are built so 
that the discharge valves may be readily removed ; these valves 
should be cleaned regularly once a week by the engineer, who 
should make sure that they fit properly. It is impossible to 
get good lubricating oil that is free from carbon, hence there 
will always be more or less carbon deposited on the discharge 
valves, but this must not be allowed to accumulate. 

" Intercoolers between air cylinders and after-coolers be- 
tween final cylinder and receiver are also recommended. The 
best intercoolers are made of nests of brass tubes, the air pass- 
ing around the tubes and the water through them, hence there 
is a thorough splitting up of the air and efficient cooling. One 
of these coolers located in the discharge pipe will absolutely 
prevent the passage of flame and will insure the protection of 
the mine against fire even though there be ignition at or near 
the air cylinder." 



Chapter XXII. 



COMPRESSED AIR IN 
MINING AND QUARRYING 



COMPRESSED AIR IN MINING AND QUARRYING. 



The rock drill as a self-acting power machine for rock-drill- 
ing is the outcome of the past half-century ; the first self-oper- 
ating percussion rook drill dates from 1849, under the Couch 
patent; since which time 
Fowle, Burleigh, Inger- 
soll, Wood, Githens, 
Rand, and Sergeant have 
improved on its design 
and brought its construc- 
tion to the present per- 
fect action. At this time 
more than a hundred 
thousand rock drills attest 
their usefulness in min- 
ing, tunnelling, and quar- 
rying throughout the civ- 
ilized world. 

Fig. 221 is a section 
of the Ingersoll drill. A, 
the shell ; B, piston with 
rotating device ; R, air 
chest ; T, bolt that holds 
the heads of the air chest 
and on which the balanced 
piston valve slides, and which is thrown by small air ports 
opened by the drill piston at the end of its stroke. 

Other models of drill valves are made by the Ingersoll- 
Sergeant Drill Company, the invention of Mr. Henry C. Ser- 
geant, among which are the tappet valve for a rock drill. The 
27 




Fig. 220.— the new ingersoll. 
On universal tripod. 



4i8 



COMPRESSED AIR AND ITS APPLICATIONS. 



ports are radial and flat, and are opened and closed by the 
swing of the valve on its centre. The valve is thrown by the 
shoulders on the piston striking the valve arms. 




Fig. 221.— section of the ingersoll. 

Another improvement is shown in Fig. 223, being an arc 
tappet valve motion, for a rock drill. The valve is moved on 
a circle radial with the tappet centre, and is thrown by the 
tappet-arm contact with the shoulders on the piston. 

Another rock drill of this company is the "Sergeant drill," 
having a piston valve as in the Ingersoll model, which is thrown 





^lve. Fig. 223.— arc tappet valve. 

by an auxiliary arc valve or ported sector that opens the small 
ports alternately behind the piston valve. The sector is thrown 
by contact with the shoulders of the central recess in the drill 
piston. It is the trigger of the main or piston valve, and opens 
or closes the air passages to the piston valve alternately. It is 




Fig. 224— auxiliary arc valve. 



so light that it is quickly and positively moved by the passing 
of the piston shoulder and held in position to near the end of 
the drill piston stroke. 



COMPRESSED AIR IN MINING AND QUARRYING. 419 



Types of Air and Steam Rock Drills of the Ingersoll- 
Sergeant Drill Co. 




Fig. 225.- the sergeant rock drill. 
In sizes 2, 2%, 3, 3^, and 3^-inch diameter of pistons. Stroke, 4^, 6%, and 7 inch. 



420 



COMPRESSED AIR AND ITS APPLICATIONS. 



Types of Air and Steam Rock Drills of the Ingersoll- 
Sergeant Drill Co. 




Fig. 226.— the ingersoll eclipse drill. 

Mounted on Sergeant universal joint tripod. 1%, 2%, 2%, 3, 3^, 3^, 
of piston. 4 to 8-inch stroke. 



and 5-inch diameter 



compressed air in mining and quarrying. 42 1 

Types of Air and Steam Rock Drills of the Ingersoll- 
Sergeant Drill Co. 




Fig. 227.— the ingersoll automatic feed drill. 

As the piston approaches the front head in cutting, it strikes a knuckle joint which turns 
a nut on the feed screw. The largest rock drill made ; 4% and 5-inch diameter ; 8-inch stroke. 
Its special application is in submarine work. 



422 COMPRESSED AIR AND ITS APPLICATIONS. 



Types of Air and Steam Rock Drills of the Ingersoll- 
Sergeant Drill Co. 




FIG. 22S.— THE ARC VALVE TAPPET DRILL. 

A positive valve motion by direct contact of the tappet with the piston. Made in the usual 
sizes of the Ingersoll-Sergeant Drill Company. 






COMPRESSED AIR IN MINING AND QUARRYING. 423 

THE BAR CHANNELLER. 

In the bar channeller has been found one of the most useful 
of the air-driven machines for quarrying dimension stone for 
building. It has been greatly developed and improved of late 
years. One of its novelties is an independent air motor that 
traverses the drill forward and back along the bars at regulated 




» _J 

FIG. 229.— THE CHANNELLING MACHINE. 

speed, thus enabling long channel cuts to be made quickly and 
with accuracy. This with the quarry bar and gadder are es- 
sential features in the operation of marble and slate quarries. 

COAL CUTTING BY COMPRESSED AIR. 

The past decade has developed great progress in the mining 
of coal in Europe and the United States, by the introduction of 
compressed air for many of the operations that before were 
tediously wrought by hand. The hand coal pick has been 
largely displaced by the introduction of the compressed air pick 
or coal-cutting machine, which is essentially a rock drill on 
wheels with a long sharp blade, by which the wall face of a 
coal seam is under-cut along the bottom of its face and shear- 



424 



COMPRESSED AIR AND ITS APPLICATIONS. 



cut in vertical seams from top to bottom by merely changing 
the small wheels to larger ones to give the pick a vertical 




Fig. 230.— compressed air coal-cutting machine. 

range. By the use of the coal-cutter a miner's work per shift 
is increased from four to six times over old methods. 

Fig. 230 is a sectional view of the Ingersoll-Sergeant Coal- 
Cutting Machine with its double piston valve movement in 
which the alternating strokes of the valves are made automatic 
by the cross connections of their ports, thus alternating the 
stroke of the main pick piston. 

Fig. 231 shows the position of the coal-cutter on an inclined 




-INGERSOLL- 



COAL-CUTTER. 



platform and the position of the operator ready for making an 
under-cut in a coal face. 



COMPRESSED AIR FOR INGERSOLL-SERGEANT ROCK DRILLS AND 

COAL-CUTTERS. 

The following table is intended to show at a glance the ap- 
proximate quantity or volume of free air required for operating 
rock drills and coal-cutters, the air being delivered to the ma- 
chines at 60 pounds pressure. 



COMPRESSED AIR IN MINING AND QUARRYING. 



425 



As applied to rock drills, these figures are necessarily ap- 
proximate only, owing to the varying conditions under which 
such work is performed ; but they will be found to apply closely 
to average conditions in rock of moderate hardness. A liberal 
allowance has been made above the actual requirements of new 
machines, to provide for wear, etc., but no allowance is made 
for leaky pipe, as this should not be permitted to exist. In 
soft material the actual drilling time is short, and more drills 
can be run with a given size compressor than where the mate- 




FlG. 232.— REAR VIEW, COAL-CUTTEI 



rial is hard and the drills running continuously for a longer 
period. 

In tunnel work in hard rock, where a high air pressure is 
carried to insure rapid progress, experienced contractors have 
found it profitable to provide compressor capacity in excess of 
the usual requirements by 25 to 50 per cent. 

For coal-cutters, the figures given are liberal, and more 
machines can probably be added where a large plant is in oper- 
ation ; but it should always be remembered that it is better 
economy to provide a large compressor and run it slowly, rather 
than a small one that has to be driven to its full capacity. This 



426 



COMPRESSED AIR AND ITS APPLICATIONS. 



fact is recognized by the best engineers, and it applies more 
particularly to a compressor than to an engine or boiler. 

The capacities in this table are based on 60 pounds air press- 
ure; if 75 pounds is used, one-fifth more volume should be 
added to the volume stated in the table ; if 90 pounds, two-fifths 
should be added. 



TABLE XL. — Cubic Feet of Free Air per Minute Required to Run from 
One to Forty Ingersoll-Sergeant Drills with Sixty Pounds Pressure. 



& a 


Rock Drills— Sizes. 


Coal Cutters. 


S "S2 






















3 2 


A 
2 inch. 


B 

2% inch. 


C 

2^inch. 


D 
3 inch. 


E 
3% inch. 


F 
2% inch. 


G 

4^ inch. 


H. 
5 inch. 


3^ inch. 


4 inch. 


1 


65 


70 


95 


IIO 


115 


125 


140 


165 


70- 


93 


2 


110 


120 


160 


190 


200 


230 


250 


280 


140 


186 


3 


156 


174 


234 


279 


294 


333 


360 


405 


2IO 


279 


4 


196 


220 


304 


356 


372 


428 


460 


524 


280 


372 


R 


230 


260 


370 


425 


445 


510 


555 


635 


350 


465 


6 


264 


294 


426 


486 


516 


588 


642 


738 


420 


558 


7 


294 


329 


476 


546 


58i 


658 


721 


S26 


490 


651 


8 


320 


360 


520 


600 


640 


720 


800 


920 


560 


744 


9 


360 


405 


5S5 


675 


720 


810 


900 


1,035 


630 


«37 


10 


400 


450 


650 


750 


800 


900 


1,000 


1,150 


700 


930 


12 


480 


540 


780 


900 


960 


1,080 


1,200 


1,380 


840 


1, 116 


IS 




675 


975 


1,125 


1,200 


i,35o 


1,500 


1,725 


1,050 


i,395 


20 






1,300 


1, 500 


1,600 


1, 800 


2,000 


2,300 


1,400 


1,860 


25 






1,625 


1,875 


2,000 


2,250 


2,500 


2,775 


1,750 


2,325 


30 






1,950 


2,250 


2,400 


2,7.0 


3,000 


3,45o 


2, IOO 


2,790 


40 






2,600 


3,000 


3,200 


3,600 


4,000 


4,600 


2,800 


3.720 



The operation of the compressed-air coal cutter depends 
upon the automatic action of a double piston valve in a valve 
chest immediately over the cylinder. The action of the valve 
pistons is alternating, each piston opening ports for its opposite 
valve, one of which is the supplementary piston. 

The illustrations will serve to give a correct idea of the ap- 
pearance of the pick machine. It is mounted on wheels 16 to 
20 inches in diameter, according to the requirements ; weighs 
from 500 to 750 pounds, and is easily moved from one place to 
another, the time consumed in moving from room to room of 
average length, including loading and unloading, being about 
ten minutes. In operation the machine is placed on a platform 
made of 2 -inch pine, about 8 feet long and 3 feet wide, which 



COMPRESSED AIR IN MINING AND QUARRYING 



427 



is so inclined toward the face by means of a trestle under the 
outer end that the recoil of the machine is neutralized by grav- 
ity and feeds down to the coal. The method of mining is as 




FIG. 233.— THE CHICAGO ROCK drill. 
The Chicago Pneumatic Tool Co., Chicago, 111., and New York City. 

follows : The runner sits on the platform behind the machine, 
which he holds by the handles ; the pick is shot against the 
coal by means of compressed air at a pressure of from 40 to 90 



428 



COMPRESSED AIR AND ITS APPLICATIONS. 



pounds, striking with a force and speed which can readily be 
adjusted to range from 160 to 250 blows per minute, at a force 
per blow at from 5 to 1,500 pounds. The runner uses a block 
attached to his shoe by a strap to chock the wheels of the ma- 
chine against the recoil. 



ROCK DRILLS OF THE CHICAGO PNEUMATIC TOOL COMPANY. 

The Chicago reciprocating rock drill is an improvement on 
the old style rock drill ; it is equipped with an auxiliary valve, 

which acts as a controller 
for the main valve, thus 
insuring a perfect valve 
movement. It is used in 
quarries, for excavating 
and tunnelling, and in 
shaft and mine work. 

The Chicago rock drill 
is a combination of a 
pneumatic hammer and a 
pneumatic drill. In the 
cylinder of the hammer is 
set a drill bit made of 
grooved steel i/% inch in 
diameter, in any desired 
length. The chuck is cut 
out to fit a cross-section 
of the drill bit, so that 
the same can be set in 
the hammer socket 
loosely, requiring no set 
screws, bolts, or pins to 
hold it in place. This 
A tube encases the drill bit, 




Fig. 234.— Chicago rock drill. 
Hammer type. 



saves much time and annoyance 

the tube encircled by a spiral, which, when the drill bit revolves 



COMPRESSED AIR IN MINING AND QUARRYING. 



429 



serves to remove from the hole, as the drill advances, all the 
cuttings of rock and other material, much after the order of the 
auger bit. There are four tongues riveted to the internal diam- 
eter of the casing, fitting four grooves in the bit, compelling it 
to rotate simultaneously with the drill. 




FIG. 235.— NO. 2% DRILL ON TRIPOD. 



ROCK DRILLS OF THE McKIERNAN DRILL COMPANY, 
NEW YORK CITY. 



The drills of this company are made in nine sizes, viz. : 2 



in., 2^ in., 3 in., 3^ in., 3^ in. 



3^3 in., and 



5 in. ; the last size being a specially arranged drill for sub- 
marine drilling. 



430 COMPRESSED AIR AND ITS APPLICATIONS. 

They are substantially constructed on the lines of the ex- 
pired Ingersoll patents, with the usual spiral bar with ratchet 
and pawl rotation, and provided with a release movement for 
obviating possibility of breakage. The cylinder heads are held 
by strong helical springs of steel braced by through rods to lugs 
at the lower end of the cylinder, thus relieving the machine 

from jar by the piston 

striking the cylinder 

head. 

One of the essential 

features of this rock drill 




is the valve, on which 

depends the action of 

the drill. The valve as 

fig. 236.-THE piston valve. shown in the cut is of 

a four-part piston type, 
turned from solid tool steel, has a perfectly balanced motion and 
moves automatcially, having no mechanical connection with the 
piston ; it being operated by air ports opened and closed by the 
alternating movement of the drill piston. An annular recess at 
the central part of the piston opens an air port for pressure and 
exhaust at the ends of the piston valve. The air pressure in 
the valve chest is between each of the ends and central discs of 
the valve, while the exhaust takes place between the central discs. 
Thus the valve is perfectly balanced and only requires its fric- 
tion to be overcome by the alternating air pressure on the ends. 
The submarine air or steam rock drill of this company has a 
cylinder of 5 -inch diameter, 8-i-inch stroke, and for the purpose 
of submarine drilling is mounted upon a wooden slide or a 
special frame to give it a long reach. The whole apparatus is 
mounted on a spud platform, or a heavy scow, and sometimes 
both when the boiler and air compressor are carried on the 
scow. In this way the drill has a more steady position on the 
spud frame, and is readily moved to new positions. 



COMPRESSED AIR IN MINING AND QUARRYING. 



431 



ROCK DRILLS OF THE PHILLIPS ROCK DRILL COMPANY, 
PHILADELPHIA, PA. 

The "Badger" drill 
is the trade name of the 
rock drills made by this 
company. The "New 
Badger" is their latest 
improvement. 

Its general construc- 
tion follows the lines of 
the best types. The 
blow of the drill is un- 
cushioned, and all the 
energy put into the pis- 
ton, less that due to the 
friction of the parts, is 
expended at the cut- 
ting edge of the bit. 
The valve is of the spool 
or piston type, operated by air ports at each end alternately 
opened by the recess in the drill piston near the ends of its stroke. 

In Fig. 239 is shown the "New Badger" drill on tripod 




. — THE BADGER DHILL. 




Fig. 238.— longitudinal section of the drill. 
Showing the figured parts which are named in their catalogue. 



+32 



COMPRESSED AIR AND ITS APPLICATIONS. 




working close to the side face 
of a rock wall, one of the 
most inconvenient positions 
for operating a rock drill. 



Fig. 239.— the "new badger. 
Working close to side face. 



THE NEW LEYNER COMPRESSED-AIR 
ROCK DRILL. J. GEORGE LEYNER, 
DENVER, COLO. 



This is a pneumatic or air drill, 
for drilling rock or ore in mines, 
tunnels, and quarries. It is unlike 
the type of rock drills that have been 
in use for nearly forty years, es- 
pecially in this, that the steel is en- 
tirely disconnected from the piston. 
That is to say, the steel, instead of 

being plunged by the piston against the rock, is struck by the 
piston and driven into the rock. 

A hardened steel tapered pin in the front end of the piston 




Pig. 240.— section of the leyner 
rock drill. 



COMPRESSED AIR IN MINING AND QUARRYING. 433 

strikes the hardened end of the shank of the drill steel. The 
weight of the piston is but a little more than one-fourth of the 
weight of the piston of an ordinary drill, but its velocity is 
about four times as great. 

The steels used for drilling are hollow. A small steel tank 
is filled with water and connected to the air line to obtain press- 
ure to carry the wa- 
ter to and through 
the drill. This tank 
is connected by 
means of a hose to a 
suitable connection 
on the back of the 
machine. A steel 
tube passes from this 
water connection 
through the machine 
and into the hollow 
drilling steel. 

A needle valve 
fitted to the machine 
gives the operator 
perfect control of the 
water supply. 

Through a valve 
in front of the chest 
air is admitted into 
the front of the cyl- 
inder, passes out through the steel, and is discharged from 
the bit into the hole being drilled, thus expelling the cuttings. 
By turning the water valve, the operator mingles a spray of 
water with the compressed air, so that the cuttings expelled 
from the hole are free from dust. 

The Leyner drill is made in two sizes, viz. : 2-l~inch diame- 
ter of piston, whole weight of drill 115 pounds; 3-inch diame- 
28 




Fig. 241.— leyner rock drill on column. 



434 



COMPRESSED AIR AND ITS APPLICATIONS. 



ter of piston, whole weight 165 pounds; ready for mounting on 
tripod or column. 



ROCK DRILLS OF THE RAND DRILL COMPANY, NEW YORK CITY. 

Fig. 242 represents the general form of the little Giant 
Rock drill, and Fig. 243 the detail of the valve gear and rotat- 
ing device in section. 

The valve of the Little Giant drill is a plain slide-valve, al- 
ways thrown in the same 
direction in which the 
piston is moving. The 
opening and closing is 
effected in a positive 
manner. 

A three-arm rocker, 
or lever, operates the 
valve and is held in 
place by a pin ; the rock- 
er is placed in a recess 
of the cylinder, between 
the ends of a double- 
headed piston, and its 
upper arm, or head, en- 
gages into the valve ; as 
the piston reciprocates 
it shoves the rocker in the direction in which it is going and 
thus moves the valve with it. 

Fig. 244 represents the piston or spool valve of the Slug- 
ger air drill. It is a three-part spool, and is operated by the 
opening and closing of small ports at the terminal strokes of 
the drill piston, and is stopped by steel spools abutting against 
soft elastic buffers. 

The Slugger drill is made in five sizes from 2^ to 3^ inch 
diameter, and from 6% to 7^ inch stroke. These drills have 




Fig. 242.— the little giant rock drill 



COMPRESSED AIR IN MINING AND QUARRYING. 



435 



the delayed action of the valve at the striking end of the 
stroke, whereby the air or steam is not admitted to the front of 
the piston until the blow is struck. The compressed air and 
steam rock drills are essentially alike in action and have a good 
record in mining, tunnelling, and quarry work. 




Fig. 243.— valve gear and rotating device 
Of the Little Giant rock drill. 



We give herewith a table of cubic feet of free air per minute 
required to operate from one to fifty Rand drills, of various 
sizes, at 60 pounds pressure at sea level and run under average 
mining conditions: 

TABLE XLL— Air Required to Operate Rand Rock Drills. 



Number or name. 


Kid. 


No. 1. 


No. 2. 


No. 3. 




No. 3%. 


No. 4. 


No. 5. 


No. 7. 


Diam. of cylinder, 
in inches. 


\*% 


2X 


2^ 


3/s 


3A 


3X 


3}i 


4^ 


sy 2 


Number of drills. 
I 


35 
61 
88 
113 
135 
158 
185 
210 
231 
256 


53 

93 

133 

170 

204 

238 

280 

3i8 

350 

387 

460 

573 

756 

930 

1, 112 

1,482 

1,855 


64 
112 

l6o 
206 
246 
288 
340 
384 
423 
466 

554 
691 
914 
1, 120 
i,343 
1,790 
2,240 


95' 
166 
238 

306 

365 
428 
504 
580 
626 
693 
822 
1,030 

1,350 
1,665 

2,000 
2,660 

3,325 






103 

180 

258 

332 

396 

463 

545 

620 

680 

750 

890 

1,112 

1,470 

1,800 

2, 163 

2,880 

3,600 


112 

196 

280 

360 

430 

505 

593 

672 

740 

817 

970 

1,210 

1,600 

1,960 

2,355 

3,140 

3,920 


132 
231 

330 

425 

508 

595 

700 

792 

870 

964 

1, 140 

1,425 

i.SSo 

2,310 

2,780 

3,700 

4,620 


154 
270 
385 
495 
592 
693 
815 
924 
1,015 
1, 122 








6 




8 

9 


12 


1.330 
1,665 


15 




20 . 




25 




2,700 
3,240 
4,310 

5,400 










50 













Following is an appendix to above table giving factor for 
determining free air per minute required at 60, 70, 80, 90, and 



436 



COMPRESSED AIR AND ITS APPLICATIONS. 



ioo pounds pressure, arid for altitudes from sea level to 10,000 
feet above : 









Factor 


of Multiplication. 






Atmospheric 
pressure, 










Altitude 










in feet above 


pounds 




Pressure at Drill. 




sea level. 


per square 












inch. 
















60 pounds. 


70 pounds. 


80 pounds. 


90 pounds. 


100 pounds. 




1+7 


I. OO 


I-I33 


I.26 


I.40 


1-535 


500 


14-45 


1. 015 


1. 15 


_1.28 


I 


425 


1.563 


I.OOO 


14.12 


I.03 


1. 17 


?i-3i 


I 


45 


1.59 ? 


I.500 


13.92 


I.048 


1. 19 


i-33 


I 


48 


iMm': 


2,000 


13.61 


I.06 


1. 21 


1-35 


I 


50 


1.645 ,-• 


3,000 


*" 13-10 


I. IO 


1.25 


1.40 


I 


55 


1.70 


4,000 


12.61 


1. 131 


1.287 


1-443 


I 


60 


1.755 


5,000 


12.15 


I.I7 


i-33 


1-495 


I 


652 


1.81 


6,000 


11-75 


I.20 


1-37 


1-537 


I 


705 


1.87 


7,000 


IT. 27 


I.24 


1.42 


i-59 


I 


76 


1.935 


8,000 


IO.85 


I.282 


1.465 


1.645 


I 


825 


2.00 


9,000 


IO.45 


I.32 


I-5I 


1.70 


I 


90 


2.07 


IO.OOO 


IO.IO 


I.365 


1.56 


1-755 


1 


968 


2.143 



Example. — Take the case of three 2% -inch drills at 60 
pounds,, at sea level. This requires a compressor with a free 




Fig. 244.— the slugger rock drill valve movement. 



air capacity of 133 cubic feet. Now if it is the desire to oper- 
ate these drills at 80 pounds, and at sea level, the free air ca- 
pacity of a compressor will have to be 133 X 1.26 = 168 cubic 
feet per minute. If the drills are to work at an altitude of 
5,000 feet, and 70 pounds pressure at drill, the free air capacity 
required will have to be 133 X 1.33 = 177 cubic feet per minute. 



THE POWER OF COMPRESSED AIR. 437 



IMPACT, OR THE FORCE OF PERCUSSION, IN HAMMERS AND 
PERCUSSION DRILLS. 

The force of a blow from a hammer in the hand, of a drop 
press, a pile driver, a hammer, a rock drill ; the falling of solid 
bodies, the water ram in pipes; and the power of projectiles, 
produce effects deducible from the general laws of dynamics 
applicable to such work. 

The power of the hand hammer, which has not as yet been 
classed among the "mechanical powers," without doubt de- 
serves the place of honor as the most ancient and, in many 
respects, the most wonderful mechanical power known. We 
daily see the results of its surprising force, effected without the 
complication of levers, wheels, or wedges ; and apparently hav- 
ing some innate power superior to and independent of the prin- 
ciples of mechanics as commonly studied. 

In order to enable any one to make the complete compu- 
tation of the velocity of a drop hammer in the drop press, a 
cushioned air hammer, or the monkey of a pile driver, when 
the velocity is due to gravity only, the power of impact at the 
moment of giving the blow may be ascertained from the known 
height at which the velocity of fall commences. The effect 
due to cushioning of air and spring hammers will be an accel- 
eration of velocity due to the^gross pressure at starting, and 
will be described later on. - — . , 

The square root of twice gravity (V04733) multiplied by the 

square root of the height (Vheight) infeet; V2 g X h, or 8.02 

X VTi = the velocity in feet per second at the instant of impact 

of a falling body. . ^ 

Then one-half the square of the velocity X by the ^ — 

gravity 

_X — , or more simply the height of fall X by the weight, gives 

the number of foot-pounds due to the fall ; and the distance at 
which the force of the blow isafre'ste&iis the measure of the 



438 COMPRESSED AIR AND ITS APPLICATIONS. 

force of percussion or impact. It is as much more than the 
momentum in foot pounds as the distance of arrest bears to a 
foot. Thus, if at half a foot the impact is twice the foot 
pounds, at i inch it is 12 times, and so on through the frac- 
tions of an inch ; at y± inch it is 48 times, and at ■£% inch 
it is 384 times. This latter arrest represents the impact of 
hardened surfaces, where the elasticity of the metals largely 
represents the small movement at impact, and of which the re- 
bound of a hammer from the face of a hardened anvil repre- 
sents the reactive effect of the foot pounds due to the momen- 
tum of the fall. 

A small hammer swiftly wielded will accomplish that which 
would otherwise require a direct pressure of several tons. 
Seeking the cause of its mystic power, the principles of accu- 
mulated work or energy stored in weight and velocity will ac- 
count for the varied effects we obtain. 

In striking a blow with a hammer upon the head of a chisel 
there are two forces brought into action, viz., the force of grav- 
ity and muscular force to increase the velocity, so that, at the 
instant of striking, the hammer may have a velocity of from 20 
to 50 feet per second; the effect at this moment is the same as 
if the final velocity had existed throughout the whole of the 
stroke. Assuming 32 feet per second as the actual velocity at 
moment of impact, then the force will be the same as if the 
hammer had fallen from a height of the square of the velocity, 

3-" 



divided by twice gravity, ( — ) 
^2 W 



= 16 feet. 



64.33 

With a hammer weighing 2 pounds, then, the accumulated 
work or energy will be 16 X 2 = 32 foot pounds. 

Supposing that the face of the hammer moves one-eighth of 

an inch after touching the head of the chisel before the energy 

is all absorbed, then the result will approximately be the same 

1 2 
as a direct pressure or dead load of 32 X -p = 3,072 pounds, 

8" 

or upward of 1^- net tons; but this is only partially true. 



THE POWER OF COMPRESSED AIR. 439 

More correctly it would be an average pressure of 3,072 
pounds, being considerably more at the commencement of con- 
tact with the chisel and reduced at the end of the chisel cut to 
the mere weight of the hammer and chisel. 

The hammer may be a self-adjusting mechanical power; for 
if the material be harder, so as to give more resistance to the 
chisel, the cut will not be so great, and therefore the force of 
percussion will be greater. For instance, if the movement of 
the chisel, as above stated, had been only one-sixteenth of an 
inch, the force would have been doubled or equal to a pressure 
of 3 tons instead of i± tons. 

But there is a limit to the effect ; otherwise the blow would 
be measured by thousands of tons, until the rigidity of the mass 
receiving the blow was balanced by the elasticity of the mate- 
rial giving and receiving the blow. This is beautifully illus- 
trated when striking the hardened face of an anvil with a ham- 
mer, where nearly the whole force of the blow is returned in 
the rebound of the hammer. 

The intensity or quality of a hammer blow is of great im- 
portance in the various materials upon which it is used ; the 
man of iron and steel using a quick blow, while the man of 
stone uses a slower blow with a heavier hammer, or the elastic 
mallet, which gives a pushing blow — each method being the 
best in its way, because suited to the material operated upon. 

When we reach the domain of "power behind the throne," 
and have steam and compressed air to aid the force of a blow, 
the elastic force behind the hammer gives it the velocity due to 
impractical height of fall in large bodies, and thus adds power 
to a short stroke, and enables that control over the movements 
of a great steam or air hammer so necessary for the successful 
working of the immense forgings now being made. The later 
improvements in hydraulic forge hammers have enabled the 
enormous hammer pressure of 4,000 tons to be utilized in 
making the forgings for modern ordnance. 

In computing the power of direct-acting steam or air-driven 



44-0 COMPRESSED AIR AND ITS APPLICATIONS. 

forge hammers, we have the elements of the initial pressure, 
from which must be deduced the mean pressure throughout the 
stroke, the weight of the hammer, rod, and piston, and the 
length of stroke, from which to obtain the positive work of the 
hammer per stroke ; against which are the back pressure from 
a cushioned blow, or the constant retarding pressure from the 
exhaust with a free stroke, together with the friction of the 
moving parts, which constitute the sum of the deductions to be 
made from the computed positive impact of the hammer. 

For the purpose of arriving at the approximate power of 
percussion of a steam or air hammer, we may assume for the 
conditions of computation a weight of 4,000 pounds for the pis- 
ton, rod, and hammer, with a diameter of cylinder of 20 inches 
and a maximum stroke of 3 feet, with air or boiler pressure at 
100 pounds. 

From the nature of the work of an air or steam hammer, 
both the pressure and stroke must be extremely variable below 
the limit of greatest capacity, so that for the maximum effect 
we have : 

W = Weight of hammer, piston, and rod = 4,000 pounds. 

S = Greatest stroke of piston = 3 feet. 

P = Pressure, area of piston 314 square inches x 50 pounds 
assumed mean pressure = 15,700 pounds. 

g = Gravity, or the velocity of a falling body at the end of 

one second of time = 32.16. 

vi = Mass = Weight divided by gravity = — = 124.378. 

32.16 

/= Total accelerating force P -f- W = 19,700 pounds. 
a = Acceleration =-t = P + W = 158.388. 

111 111 

v = Velocity of impact == 

a/ 2 a 3 _ 2 s — — — = 3°- 82 7 f eet per second. 

"t .. m ■ ■"- 

r ,;E = Energy = - , -i ri: 

m2S (l±^L) <4™ 

m v 2 ^ m ) 



r^.'S ; P 4- S W = 59, 100 foot-pounds. 



THE POWER OF COMPRESSED AIR. 441 

If the energy of the blow is arrested by the compression of 
the forging- and the spring of anvil in a distance of one inch 
from the point of contact, the measure of the force of percus- 
sion must be multiplied by the distance of arrest in fractions of 
a foot for its true value. Thus for one inch 12 X 59,100 = 
709,200 pounds, or over 354 tons = the static pressure due to 
percussion. 

In striking a cold mass of iron upon the anvil block with a 
yield of only one-quarter of an inch the enormous pressure of 
over 1,400 tons would be attained. 

From the total accelerating force, the friction of piston, rod, 
and slides should be deducted; amounting in well-constructed, 
direct-acting hammers to from 3 to 5 per cent. The resistance 
to the power of a full hammer blow from the back pressure of 
the exhaust is of some importance, and may possibly amount to 
from 3 to 5 pounds per square inch, or about 10 per cent on the 
total effect, as above stated. 

The effect of cushioning of the piston is a beautiful illustra- 
tion of the control that can be made over an intense mechanical 
force, that by the mere movement of a hand may have its 
power varied from o to a percussion pressure of over 1,300 tons. 

The action of a rock drill is somewhat unique in its persist- 
ence in overcoming the resistance of the various kinds of rock 
to its efforts to penetrate their depths. It does its work not so 
much, by the high percussion pressure of a single blow, but 
rather by the quick repetition of blows just suited for effective 
work and for accomplishing a given depth of hole in the shortest 
possible time. Its peculiar valve gear and short stroke make 
its percussive force almost wholly due to pressure on the pis- 
ton, which is made thoroughly controllable at the hand valve 
and feed screw. By this means the drill may be run at a 
stroke and pressure that gives the fastest cutting power; and 
as this may not be its longest stroke,, which cushions the blow 
and reduces the number of blows per minute, a medium of from 
75 to 85 per cent, of the full stroke is found to be most effective. 



442 COMPRESSED AIR AND ITS APPLICATIONS. 

The friction of the drill steel in the hole, added to the fric- 
tion of the piston rod, piston, and rotating device or rifle bar, 
is a serious drawback to the otherwise large theoretical power 
of percussive pressure in the rock drill. 

Take, as an example, the theoretical percussive blow from 
a medium size rock drill of say 3 inches diameter of piston, 
running at 60 pounds pressure with 5 -inch stroke, having an 
effective piston area, after deducting the area of the rifle bar, 
of 6 square inches ; weight of piston and drill steel, 50 pounds. 

The friction of the pipe and passages, throttling by the 
valve and back pressure from the exhaust, together with the 
following of the steam or air pressure for three-quarters of the 
stroke, will reduce the mean pressure to 40 pounds. 

Then by the formulas as given for the steam or air hammer, 
the energy of the blow will be the total mean pressure on the 
piston multiplied by the stroke in fraction of a foot, plus the 
stroke multiplied by the weight, or 6 square inches X 40 pounds 
X tt + A X 5° pounds = 120.83 foot-pounds. 

Then if the drill penetrate the rock \ of an inch at each 

1 2 
stroke the theoretical effect of percussion will be : — or 96 X 

i 
120.83 = 1 1.699 pounds, or nearly 6 tons static pressure. 

A large allowance from the theoretical effect must be made 
for the actual effect, by the assumed value of the friction of the 
drill steel on the sides of the hole, and other moving parts, as 
well as for the resisting effect of water and debris of drilling, 
which always more or less clog the drill hole. 

The average running time of drills on open rock work is 
about five hours per day, and the average of 250 strokes per 
minute or 75,000 strokes per day is probably a fair average 
day's work. This at ^--inch depth of cut and 10 strokes to make 
a circuit of revolution of the steel to complete the cut will rep- 
resent ill = L — = 78 feet lineal depth of holes for a day's 

96 10 

work in rock of medium hardness — limestone. In granite from 



THE POWER OF COMPRESSED AIR. 443 

50 to 60 feet is about an average day's work, owing to the less 
penetration of the drill per stroke ; while in marble, with dry- 
short holes, a very much larger depth of holes, 200 to 250 feet, 
has been drilled. In this kind of work the actual running time 
of the drill is increased by the increased facilities of adjustment 
from hole to hole and the use of only a single drill steel. 

The principles governing the force of a blow may be ap- 
plied to the air hammer as used for chipping or riveting. The 
entire elimination of slides and drill friction in the air hammer 
leaves only the friction of the piston to be considered, and this 
is so small that 5 per cent of its percussive power is ample to be 
deducted from its total computed static pressure. A i|--inch 
hammer piston, weighing 2 pounds, with 4-inch stroke, running 
with 60 pounds air pressure, will have 1.76 square inches X 60 
X -g- foot = 35 -f 2 X{= 35-66 foot-pounds per blow, less 5 
per cent = 33.8 foot-pounds. If the chisel moves forward -^ 
inch at each blow, then 33.8 X 16 X 12 = 6,489 pounds is the 
static weight equivalent to each blow. Then if the hammer 

makes 500 blows per minute, - — = 31 inches would be the 

16 

length of chip cut per minute ; and so on for any work of per- 
cussion by air hammers. 



Chapter XXIII. 



PNEUMATIC TOOLS. 

THE PNEUMATIC HAMMER 

AND ITS WORK 



PNEUMATIC TOOLS. 

THE PNEUMATIC HAMMER AND ITS WORK. 

The engineering industry at the present time is enjoying 
a period of activity quite unprecedented in its history, and, as 
a consequence, is calling for an immense increase in the num- 
ber of its labor-reducing machines. Prominent among these 
are portable pneumatic tools and appliances, and it is not too 
much to say that there is every indication of their extended 
application. They have been used for a considerable time, al- 
though, with certain exceptions, they have not been well ap- 
preciated until the last few years, and considering their impor- 
tance and the valuable assistance they are rendering to the 
shipbuilding and man)' other industries, it is somewhat singular 
that comparatively little information has been circulated about 
them except by trade descriptions. Doubtless some explana- 
tion for this is to be found in the fact that their practical appli- 
cation is of comparatively recent date, and further, that some 
of the earlier tools were unsatisfactory. Whatever the cause 
may be, it appeared that the subject was one which would be 
of vital interest in its relief to the weary muscle of the me- 
chanic. The author, at the same time, is aware that the sub- 
ject is by no means a new one to some of the leading and more 
enterprising firms, who have experimented with pneumatic 
tools for some years past ; and he also recognizes that certain 
kinds of portable pneumatic riveters and other appliances have 
been in constant use for a considerable time, but he ventures 
to hope that the various tools described and illustrated in this 
work may be of interest, as showing what has been achieved 
up to the present date. The various tools which can be driven 



448 COMPRESSED AIR AND ITS APPLICATIONS. 

by compressed air are many, and are rapidly increasing in 
number. 

Since the mechanism employed for utilizing compressed air 
to secure a percussive action is essentially the same in both 
hammers and riveters, it will be sufficient to describe the mech- 
anism in the different kinds, and for this purpose the hammer 
will first serve. 

Hammers may broadly be divided into two types, viz., the 
valveless hammer and the valve hammer. This is a convenient 
description, yet perhaps not strictly correct, because although 
the valveless hammer has no valve beyond the striking piston, 
this is itself a valve to effect the proper admission of air to 
alternate ends of the working cylinder; while in the valve ham- 
mer a reciprocating valve, working either at right angles to or 
parallel with the striking piston, acts in combination with it to 
regulate the inlet and exhaust of the compressed air. 

Valveless hammers have essentially a short stroke, and, al- 
though economical in air consumption in relation to the number 
of blows given, they will not compare with valve hammers in 
giving powerful blows which are necessary in heavy chipping 
or riveting. Owing, however, to their simple construction, 
they have probably a longer life than the valve hammers, and 
for such purposes as beading flues, light calking and chipping, 
and especially carving in stone, etc., they compare very favor- 
ably with valve hammers. The speed of the valveless hammers 
is very high, being 1,000 to 2,000 strokes per minute. 

Valve hammers will probably secure the market for general 
and heavy chipping, calking, and riveting. Their speed for 
ordinary work ranges from 1,500 to 2,000 blows per minute, 
although they can be driven much faster. Their stroke, how- 
ever, is considerably longer than that of the valveless hammers 
and the blow struck correspondingly greater. There is more 
air lost in the ports, but other advantages, including better con- 
trol for using the air expansively, overcome this small defect. 
It is well known that the nature of a blow — whether light or 



PNEUMATIC TOOLS. 



449 



heavy — on various materials, produces an effect apart from the 
actual work done as measured in foot-pounds. For example, 
10,000 small blows representing a certain number of foot- 
pounds might fail to produce a desired result, which a smaller 
number of heavy blows, representing less energy in foot- 
pounds, would effect. Having now considered the claims and 
advantages of the different types of hammers, all of which it 
may be stated can be worked economically at from 60 pounds 
to 80 pounds per square inch, reference must be made to the 
illustrations in order to explain their construction and action 
under compressed air. 

Fig. 245 shows in section a " Ross " hammer in which the 
striking piston becomes the valve to control the admission and 




FIG. 245.— ROSS PNEUMATIC HAMMER. 

exhaust of the working fluid. A represents the outer casing, 
made from solid drawn steel tube, bored and fitted with a phos- 
phor-bronze liner, B, which forms the cylinder in which the 
piston works ; E the striking piston made from a steel forging, 
ground to fit the cylinder; D, the exhaust ports, open to the 
atmosphere through the valve G , C and C l the admission ports, 
admitting compressed air to alternate ends of the piston ; K, 
another port always open to the air supply; G, the exhaust 
valve; H, the trigger actuating the same; F, the phosphor- 
bronze handle, to which compressed air is admitted at the point 
F l ; L, a piston cushion, has always full and constant pressure 
behind it from the air supply through the port U ; and M 
shows the working tool. 

It must be noted that this hammer is caused to work by the 

29 



45° COMPRESSED AIR AND ITS APPLICATIONS. 

opening of the exhaust and not by regulation of the admission. 
The direction taken by the air under pressure when connected 
to the handle at F 1 will be readily seen by noting the arrows. 
The piston is slightly reduced in diameter in the middle, and 
the inside edges of the two collars thus produced form the cut- 
off edges for pressure, while their outsides govern the exhaust 
ports. It will be seen that when the piston is in the middle of 
its stroke there is a dead point, the compressed air finding admis- 
sion only to the chamber formed by the reduced portion of the 
piston, since the ports C and C l are all cut off from admission 
of compressed air, but this does not interfere with its proper 
working, as the port cover is very small. Moreover, when 
starting, the piston will fall either to one end of the cylinder or 
the other by gravity, and when at work the momentum carries 
it over the dead point. The cut shows the front exhaust valve 
open, and the piston just commencing to make its forward 
stroke. Air flows through K, thence through the port C, pass- 
ing between the annular space formed between the liner and 
the outer casing, and back through C l to back of piston, thus 
driving it forward. At the same time, exhaust takes place 
through D. The same action takes place on the backward 
stroke, when the forward ports, C and C\ are then in commu- 
nication with K. In order, as far as possible, to eliminate 
vibration, a condition which is present in all hammers, the 
cushion piston, L, has been introduced at the rear of piston. 

Fig. 246 shows in section a " Q and C " single hammer. A 
represents a bronze handle, in which is fitted the steel liner, B, 
which forms the working cylinder; C, the striking piston, 
which acts as its own valve ; D, the outer cap, connecting the 
liner to the handle ; E, the throttle valve ; F, the trigger actu- 
ating the same ; and G, the point to which the air supply is 
attached. The action of the hammer, on the trigger being de- 
pressed, is as follows: 

The air having passed the valve, E, flows along the passage, 
d, and through a large air port into the cylinder or pressure 



PNEUMATIC TOOLS. 



451 




Fig. 246.— q and c hammer. 



chamber; this has the effect of maintaining a constant pressure 
under the shoulder of the piston and tends to drive it back- 
ward. When, however, the ports b, in the piston C, which 
are also large openings, come 
into communication with the 
cylinder, the pressure fills the 
hollow portion of the piston 
and the cylinder in its rear, 
driving the piston forward to 
strike its blow. At this in- 
stant the piston ports come 
into communication with the 
exhaust port c, when the press- 
ure under the piston shoulder again returns the piston, and 
the blows are repeated in rapid succession — as many as 1,000 
to 2,000 per minute. It will be noticed that in this arrange- 
ment of ports the air is used expansively. The same type of 
hammer is made in a modified form, being provided with a 
second piston placed in the rear of the other, the actuating 
fluid working between the two pistons for the forward stroke. 
It is claimed for this that vibration is reduced to a minimum. 

Fig. 247 shows a hammer constructed on similar lines as 
the " Q and C " with the addition of a counterbalance piston, 

which by its reaction and 
cushion relieves the body of 
the hammer and the hand 
from excessive jar. 

In the duplex riveter 
(Fig. 248) the striking pis- 
ton, A, is encased in a strik- 
ing cylinder, C, so that the tool, T, receives a blow alternately 
from the hammer piston, A, and from the cylinder, C, on the 
tool socket, H. The method of operation is shown by the 
differential piston areas. By the alternating motion and stroke 
of the two pistons the hand is relieved from jar. 




-COUNTERBALANCED HAMMER. 



452 



COMPRESSED AIR AND ITS APPLICATIONS. 




THE DUPLEX RIVETER. 



Coming now to the valve hammers, to describe them briefly 
and the same time accurately is not an easy matter, because 
although they are simple in action and not excessively compli- 
cated with regard to the 
number of working parts, yet 
their movements and arrange- 
ments of ports are such as to 
make their description some- 
what difficult. 
The "Little Giant" Hammer. — This is illustrated in 
Figs. 249 and 250, to which the following reference applies: A, 
working cylinder ; B, piston hammer ; D, working tool ; E, con- 
trolling valve; E\ steel seating for same; F, handle; G G\ 
throttle valve bushing ; H, throttle valve ; J, trigger actuating 
same; a, bore of cylinder; a 1 , passage leading from cylinder to 
top of valve chamber; a\ passage from front end of cylinder to 
annular space in valve chamber; a\ exhaust passage at rear end 
of cylinder leading to exhaust through interior of valve ; a b , 
bye-pass from a 2 ; a, exhaust passage in forward end of cylinder 
to atmosphere ; b, reduced portion of striking piston ; b\ annular 
chamber formed by such portion ; e, opening into the control- 
ling valve bushing; e\ opening into cylinder from valve bush- 




FlG. 249 - LITTLE GIANT HAMMER. 

ing; e 3 , annular portion in valve bushing; e\ openings in valve 
E, leading to exhaust port, e 6 ; c\ central chamber of valve; e% 
exhaust to air in handle; e\ enlarged diameter of valve for 
cushioning; e\ recess behind e*; e 10 , small boss on top of valve. 
Fig. 249 represents a longitudinal sectional elevation of a ham- 



PNEUMATIC TOOLS. 



453 



mer with the striking piston at the rear end. Fig. 250 is a 
similar view, but of the opposite half, and showing the striking 
piston at the forward end of stroke. Figs. 251 and 252 show 
the handle and valve portion in section with the valve at the 
top and bottom positions respectively. 

The action of the tool is as follows: air under pressure 
having been admitted by operating the valve H, passes through 
the opening e, and under the head of the valve E, thus forcing 
it in the position shown in Fig. 251. The air is then able to 
pass into the cylinder through the opening e\ and thus forces 
the piston forward into the position shown in Fig. 250. It will 




^^J kLJuE 



V\A/ 



Fig. 250.— little giant. 
Piston down. 



be noted that the piston is reduced in diameter at b, which to- 
gether with the cylinder forms a chamber, b\ so that as the 
piston nears its forward limit of stroke, air pressure enters the 
chamber b\ from the passage a\ which is in direct communi- 
cation with space e. At the same time the passage a* is 
brought into communication with b\ and thus the air passes 
along to the top of the valve E, and forces it into the bottom 
position, as shown in Fig. 252. When the valve is in this posi- 
tion a clear way for the compressed air is open to the front end 
of piston through e, e\ and a\ thus effecting the return of the 
piston. Thus far the live air admission has been dealt with to 
drive both piston and valve in both directions. Coming now 
to the exhaust and taking the piston in its rearward motion 
first, the air escapes along the passage a\ and through the 
openings, c\ in valve and out through c\ In its forward mo- 



454 



COMPRESSED AIR AND ITS APPLICATIONS. 



tion the piston exhausts first through a\ which leads direct to 
outer atmosphere. When a 1 is passed, the air escapes through 
a\ which is open to atmosphere through e 3 , e\ and e\ when the 
valve E is up. The exhaust of the valve is effected thus: 
During the backward movement of the piston, and as its annu- 
lar portion is passing a\ it permits the air pressure on top of 
valve E to escape through a 2 , a\ into b\ a\ and a\ to atmos- 
phere, with the result that superior pressure under valve head 
from e again lifts the valve. The valve is forced into its bot- 
tom position due to its area on the top being larger than the 




FIG. 25T.— LITTLE GIANT. 
Ready to strike. 



Fig. 252. -little gian' 
Return stroke. 



ring underneath its head. It is obvious that both the striking 
piston in its backward stroke and the valve in both directions 
should receive some form of cushioning, so as to reduce shock 
and prevent injury to valve and cylinder. In the piston this 
is effected by its closing the port a\ before the end of its stroke. 
In the valve the desired cushioning is secured in its upward 
stroke by means of the boss c x \ which causes the air to escape 
rather slowly into a\ In its downward stroke the cushioning 
is effected thus : The portion e 9 of the valve E is of diameter 
nearly equal to the small bore of the valve bushing, and there 
is also provided a small groove, c\ Fig. 251. When the valve 
is moving down, the portion <? 8 first enters the small bore of 
the valve chamber, and this tends to retard the passage of the 



PNEUMATIC TOOLS. 455 

air through the bore, and permits the excess of air to act as a 
cushion. Up to a certain limit the same hammer may be used 
to give light or heavy blows, and this may be effected by regu- 
lating the amount of opening given to the throttle valve. It is 
not desirable, however, simply to rely upon the trigger to do 
this, but preferably to provide a regulator, so that however 
hard the trigger may be pushed it only opens the valve the de- 
sired amount. In the " Little Giant " hammer this result is 
obtained by making the throttle valve bushing in two portions, 
G and G \ The part G is fixed to the handle, while G ' is capable 
of being screwed in or out. The effect of this adjustment, 
when taken in combination with the valve H and the trigger 
/, is such that when G l is unscrewed, the port g 1 may be 
moved into such a position that the valve H can be pushed by 
the trigger 1 to the limit of its stroke without uncovering the 
port g x at all, and by adjustment of the part G 1 any desired 
opening may be given for the admission of air. In order to 
put the valve H in equilibrium a small opening admits the 
compressed air to either side of it, which, together with the 
spring shown, effects the desired result. It will be obvious, 
that fewness of parts, and especially of joints, are desirable in 
the construction of a tool using compressed air at high press- 
ure, since the possibility of leakage is thereby considerably 
reduced. Another feature of this hammer is the economical 
use of the compressed air, due to the cushioning of the moving- 
parts taking place on the exhaust air rather than from the ad- 
mission of live air, and taking this in connection with the solid 
construction of the valve, the same being well cushioned in 
both directions of its travel, the "Little Giant" type is likely 
to prove both an economical and a good wearing hammer. 

The " Boyer " Hammer. — Figs. 253 and 254 show sectional 
views of a Boyer hammer, in which the following letters of 
reference indicate the various parts referred to: A, the work- 
ing cylinder; A the handle; G, the air passage from throttle 
valve to cylinder; G\ throttle valve; H, trigger actuating 



456 



COMPRESSED AIR AND ITS APPLICATIONS. 



same; /, the valve block; P, cap at end of same; K, the work- 
ing tool; M, the piston, consisting of a solid piece of turned 
steel fitting the bore of the cylinder and provided with a recess, 
M 1 ; O, the valve; P, passage from cylinder to small space e\ 
Q, passage from cylinder to small space n ; R, passage from 
front end of cylinder to small space m\ S, port leading from 
space e to front of cylinder through passage R; T, passage 
from cylinder through U to spacer; T\ from air supply to 
cylinder ; X, from air supply to e. 

X is only necessary to supply air to front end of piston via 
5 and R and to hold the valve in rear position. Other letters 




FIG. 253 - THE BOYER. 
ston down. 

on the drawings are referred to in the following description of 
the working of the hammer : 

Fig. 253 represents the piston in its forward and the disc 
valve in its rearward position. The compressed air having been 
admitted, passes along the passage G, and then into space e\ 
and acts on small area, d, of the disc valve O, and tends to 
force the valve forward, but air pressure in space e, admitted 
by the passage X, acting upon the large area of the valve, will 
hold the valve in the rearward position against the pressure 
acting on the small area. The air will pass from space e, 
through passages vS and R, to the front end of the piston, driv- 
ing the latter backward, the rear end of the cylinder being open 
to exhaust through the slots in valve O and groove h, the lat- 
ter being constantly open to the atmosphere through passages 




PNEUMATIC TOOLS. 457 

j, k. As the piston moves backward, it uncovers ports P and 
Q, and the pressure in front end of cylinder will exhaust 
through the groove and passages,/, k, to the atmosphere; the 
front end of the passage P will be uncovered by the front end 
of the piston at the same time as the front end of the passage 
Q, and the air in space c will escape through passages P Q, 
groove n, and passages 0, i, j, k, to the outer air. Passage P 
being larger than passage X, by which the air is supplied to 
■ the space e, the pressure on the large area, c, of the valve O 
will be greatly diminished, so that the pressure acting on the 
small area, d, of the valve O will force the valve forward to 
the position of Fig. 253, 
whereupon the ring of the 
valve O will close the pas- 
sage X, and cut off the sup- 
ply of air to space e, there- 
by permitting pressure to 
hold the valve in the forward 
position. As the piston moves forward and finally strikes a 
blow on the chisel, the air in front can escape through passage 
Q until the latter is closed by the front end of the piston, and 
thereafter can escape through passage R, grooves ;;/, a, and n, 
and passages 0, i, j, and k, to the atmosphere. The recoil ac- 
complishes most of the return of the piston. During the back- 
ward movement of the piston, the end of the cylinder is open 
to exhaust through slots /, in the valve O, and groove //, and 
passages i, /, k, until the passages P and Q are uncovered by 
the front end of the piston, at which time the valve opens, and, 
admitting air, arrests the piston and drives it forward. Al- 
though communication between T and T 1 is cut off almost di- 
rectly the piston commences its backward movement, the valve 
O will not change its position — from rear to front — because 
sufficient air pressure is passing into space e through passage X 
to hold the valve, notwithstanding the escape of the air via S, 
since the latter is of less capacity than X. It will be readily 



!54.— THE BOYER. 
Piston up. 



458 



COMPRESSED AIR AND ITS APPLICATIONS. 



understood that the action of the compressed air along the pas- 
sage G, acting first on one area and then on another area of the 
valve O, drives it in alternate directions, and that the valve in 
turn admits air to either end of the cylinder; at the same time 
the piston opens and closes certain ports in the cylinder, as in 
the case of the valveless hammer, and the combination of the 
dual motions of the valve and the piston produces the desired 
result of causing the piston to rapidly reciprocate and deliver a 
number of blows upon the tool. In this hammer it will be 
noted that the striking piston passes through the valve, which 
has the effect of increasing the stroke of the piston as compared 
with the original design of the hammer, in which the valve 




Fig. 255.— the tilden pneumatic hammer. 



was arranged in a separate chamber immediately in the rear of 
the piston chamber, and without increasing the over-all length. 
In order to effect a cushion on the piston on the rearward 
stroke, live air is admitted before such stroke is completed. 
With regard to the valve, owing to its extreme lightness and 
shortness of stroke, cushioning of the valve is unnecessary. 

The Tilden pneumatic hammer is illustrated in section by 
Fig. 255, which shows the general construction and also the 
oil chamber in the handle, which measures out and delivers 
a constant supply of lubrication to the incoming air. The re- 
ciprocating piston and valve are thereby constantly lubricated, 
a condition that of course increases the effectiveness and dura- 
bility of the working parts. This tool is manufactured by the 
International Pneumatic Tool Company, of Chicago. 

The sectional view herewith gives an idea of its construction 



PNEUMATIC TOOLS. 459 

and operation. Starting with the parts in the position as illus- 
trated, the motive fluid or compressed air from the main cham- 
ber passes through ports into the valve block chamber to press 
upon the upper end extension of the impact piston, and acting 
against the decreased area thereof imparts a light initial move- 
ment to the piston, which from practical experience is found to 
be very efficient in reducing the amount of jar or vibration. 

Otherwise, the air ports and passages are .similar in arrange- 
ment for operating the hammer piston as in other direct- 
acting hammers. 

PNEUMATIC TOOLS OF THE CHICAGO PNEUMATIC TOOL COMPANY. 

The " New Boyer " air hammers as now made are the out- 
come of several years of experiment to overcome the vibration 
of the older tools upon the hand and arm of the operator, 
when in use, as well as to simplify their construction and opera- 
tion. Fig. 256 shows the four sizes of their short-stroke ham- 
mer as now made, with samples of chisels and calking tool. 

The outcome of these trials is a modification of the hammer 
which greatly simplifies the construction. The proportions of 
certain operating parts have been altered so that the vibration 
is reduced to a minimum. The hammer is styled the "New 
Boyer" to distinguish it from the old form, which, is still sup- 
plied to the trade if desired. 

The general appearance and dimensions are not altered, the 
difference being in the operating valve. The valve mechanism 
of the new hammer is entirely different from the old, consisting 
of a single moving part; namely, the valve itself, which is 
formed of a thin cylindrical shell placed in the piston chamber, 
the piston travelling within the valve. By this arrangement a 
much longer piston chamber is obtained, hence a longer stroke, 
without increasing the length of the tool; also, the piston is 
cushioned at either end of the stroke. With a longer stroke 
the force of the blows of the piston is increased, and hence the 



460 COMPRESSED AIR AND ITS APPLICATIONS. 

new hammer has about one-third more power than the old. 
The substitution of a simple piston valve for the complicated 
arrangement previously used insures a longer life for the ham- 
mer and fewer repairs. The regulating mechanism in the 
handle is not changed. For the best working of these ham- 
mers an air pressure of 80 pounds per square inch is recom- 
mended, but they can be operated with pressures varying from 
20 to 100 pounds. 

These hammers are made in four different sizes suitable for 



1 




U I m M I 

U ' u d \ 

Fig. 256.— the "new boyer " air hammers. 

chipping, stone-carving, lettering, or tracing on marble or 
granite. 

The No. 1 New Boyer hammer weighs 10 pounds, has 4-inch 
stroke at an estimated speed of 2,000 strokes per minute, and 
in operation requires about 20 cubic feet of free air per minute. 
This hammer is especially adapted to heavy work in chipping 
and calking, and also to light riveting, and has a capacity of 
driving up to -|--inch hot rivets. 

The No. 2 New Boyer hammer weighs 9 pounds, has 3-inch 
stroke at an estimated speed of 2,500 strokes per minute, and 



PNEUMATIC TOOLS. 46 I 

in operation requires about 20 cubic feet of free air per minute. 
This hammer is adapted to general use in chipping in iron and 
steel, and for calking on ship and boiler work. For chipping 
only, it is equipped with chisels having hexagonal shanks, and 
for calking, or for calking and chipping, where it is desired to 
use the hammer for both purposes, it is equipped with chisels 
having round shanks. 

The No. 3 New Boyer hammer weighs 8 pounds, has if-inch 
stroke at an estimated speed of 3,000 strokes per minute, and 
in operation requires about 20 cubic feet of free air per minute. 
This hammer is especially adapted to beading locomotive flues 




Fig. 257.— the boyer long-stroke riveting hammer. 

and to light calking. It operates best at an air pressure of 75 
to 80 pounds. Will bead two flues per minute. 

The No. 4 New Boyer hammer weighs 7 pounds, and is 
designed for very light work such as tank riveting. 

Reputable concerns report that for chipping castings one 
man with a pneumatic hammer does the work formerly per- 
formed by three men. Fire-boxes are cut out with the aid of 
these tools in two and one-fourth hours, where the same work 
was previously done by contract, and eighteen and one-half 
hours allowed, while a total saving of ten and one-half hours on 
each fire-box is made by their use. 

The Boyer long-stroke hammer (Fig. 257) is adapted to all 
kinds of rivet work up to i-inch diameter of rivets. It weighs 



462 COMPRESSED AIR AND ITS APPLICATIONS. 

18 pounds, and has a 9-inch stroke at an estimated speed of 800 
strokes per minute. This is the most powerful pneumatic 
hammer made, and will meet the most difficult requirements. 

The new No. o long-stroke hammer of this company weighs 
13 pounds, and has a 5 -inch stroke with an estimated speed of 




Fig. 258.— the pneumatic hold-on. 

1,800 blows per minute. Its most useful work is in chipping 
and driving rivets up to f inch. 

The hold-on (Fig. 258) has a piston and pressure air spring, 
and is also provided with an extension bar to hold it in position 
in confined places. 

THE PNEUMATIC HAMMER AND ITS WORK IN STONE DRESSING. 

Perhaps the most marked improvement in the stonecutter's 
art since the stone age has been the introduction of the use of 
compressed air. For centuries the hard, unyielding stone had 
been fashioned into shape by the ceaseless efforts of the ham- 
mer and chisel; and while other trades adopted newer and 
cheaper methods of manufacture in rapid succession, no means 
could be devised to hasten the tedious processes of stone-cutting. 

The arm of the carver could deliver only a comparatively 
small number of blows per minute, but by the use of pneumatic 
carving tools this number was multiplied to such an extent that 
the blows following each other in rapid succession are in effect 
one continuous blow. 



PNEUMATIC TOOLS. 



463 



As the cutting power is always ready, the carver had merely 
to guide the machine and chisel. He can thus give his whole 
attention to his work, and the result is shown in the increased 
amount of work accomplished, and the work is done much 
better. 

A machine for surfacing granite and other hard stone is in 
use in which a powerful pneumatic hammer is mounted on a 
radial arm, which is in turn supported on a vertical column or 




THE PNEUMATIC HAMMER IN STONE DRESSING. 



post, and is moved in a plane for the operation of the dressing 
tool in any required direction. 



THE PNEUMATIC HAMMER AND ITS WORK IN SCULPTURE. 

The beautiful work of the sculpture's art has now a hand- 
maid in the pneumatic tool, which is achieving wonders in the 
rapidity of its producing power. The relief to the weary arm is 
a helper to artistic thought, and the labor of the artist does not 
hang heavy on his mind. In this way, modern sculpture should 
not only advance in its output of volume, but should rise to a 



464 



COMPRESSED AIR AND ITS APPLICATIONS. 



higher degree of perfection by the relief from irksome muscu- 
lar labor, and freedom of mind for the inception of beauty of 
thought and its transfer to the rigor of stone. 



,.«, 




I 111-. I'Nlvl M VI IC ilAM.MI K IN MIIJ'TIUK. 



THE PNEUMATIC HAMMER IN THE PATTERN SHOP. 

A Pneumatic Fret-Saw. — There has recently been made a 
new and interesting application of the pneumatic tool. This is 
a fret-saw directly attached to the piston of a pneumatic ham- 
mer and making from 1,000 to 1,800 strokes per minute. The 
saw is an ordinary keyhole-saw blade, and it may be made to 
follow the most difficult lines, of course cutting rapidly. Be- 
sides the evident use of the tool for the patternmaker and the 
cabinetmaker, it may be noted that it is employed in one of the 
largest packing-houses in Chicago for sawing ham bones, using 
a special saw with very fine teeth. This device has recently 
been brought out by the Chicago Pneumatic Tool Company. 



PNEUMATIC TOOLS. 



465 




Fig. 261.— pneumatic fret saw. 
THE PNEUMATIC HAMMER IN THE MACHINE SHOP. 

Probably in no place else can the pneumatic hammer, and 
also the pneumatic drill, be applied to so many and so varied 
classes of work as in the machine shop. A line of air pipe 




Fig. 262.— the pneumatic hammer in the machine shop. 



3° 



466 



COMPRESSED AIR AND ITS APPLICATIONS. 



along the ceiling over the vice-benches, with the air hose at- 
tached to a hammer and a drill, standing upon the bench, 
ready for instant use, is the modern exemplification of economy 
in the production of machinery and manufactured goods, that 
has given the Western world an advanced position in the pro- 
duction and distribution of machinery used in the producing 
industry of all nations. 

THE WORK OF PNEUMATIC TOOLS. 




Held up on skids. On fr; 



RILL IN SHIP WORK. 

for bottom drilling. 



The following illustrations show methods of using pneu- 
matic tools in the various parts of the constructive work in ship- 
building; to these tools our steel ship-building interests owe 
much of their competitive success. 



THE WORK OF PNEUMATIC TOOLS. 



467 





I j 



468 



COMPRESSED AIR AND ITS APPLICATIONS. 







< 







THE WORK OF PNEUMATIC TOOLS. 



469 





Fig. 269.— the long-stroke boyer in ship work. 



470 



COMPRESSED AIR AND ITS APPLICATIONS. 



THE PNEUMATIC HAMMER AND DRILL IN SHIP-BUILDING. 



The air hammer as a riveter on a balanced transverse beam 

with a ratchet stay or guide, is 
one of the late appliances for 
holding and steadying the 
hammer in deck riveting, 
and is illustrated in Fig. 270, 
while its method of operation 

PIG. 2 7 >.-THE BALANCE BEAM. j g ghown J n F j g< 2? ^ 

It is one of the handy devices lately invented for the rapid 
work of deck riveting and for relieving the muscular effort of 
holding the hammer in constant and continuous work. 





Fig. 271.— the balance beam in deck riveting. 



THE WORK OF PNEUMATIC TOOLS. 



471 




Fig. 272.— drilling and riveting in ship-building. 





Fig. 273.— the rivet hammer and hold-on in bulkhead work. 



472 



COMPRESSED AIR AND ITS APPLICATIONS. 




Fig. 274.— structue 




Fig. 275.— the yoke riveter. 




Fig. 276.— the long yoke riveter. 



THE WORK OF PNEUMATIC TOOLS. 473 



THE BOYER RIVETER IN STRUCTURAL WORK. 

No other improvement in the means of erection of modern 
structural work is so convenient and so economical as are 
compressed air tools. The air hammer and its mate, the air 
drill, have come to meet the needs of the times for quick work. 
This wonderful saving in time, which is a most important ele- 
ment in the erection of the great steel structures of modern 
days, has given an impulse to this class of structure that is felt 
throughout the civilized world, a niarvel to all nations. 

Probably no other class of construction tools has comein to 
use in a single decade, that has contributed so large a share to 
the relief of muscular labor in the new method of building with 
steel interframing, as the compressed-air tools. Their porta- 
bility and the later methods of compressing air by portable 
compressors have gone hand in hand in this progressive age of 
building. 

THE CHICAGO COMPRESSION RIVETER. 

The compression riveters, Figs. 277 to 280, are unique 
tools for their special work. They embody in a compact form 
their own hold-on, and are operated by an air piston of large 
area pressing upon a hydraulic piston of small area, which 
pressure is transferred to the piston of the riveting plunger 
at right angles, thus generating the immense pressure required 
to compress a rivet at one stroke. These compact and power- 
ful tools are hung and balanced on yoke slings and are easily 
managed in any position. The transfer medium between the 
right-angled pistons is oil with cupped leather packings on the 
pistons. 



474 



COMPRESSED AIR AND ITS APPLICATIONS. 








THE WORK OF PNEUMATIC TOOLS. 



475 





476 COMPRESSED AIR AND ITS APPLICATIONS. 



p^,- - 




Fig. 281.— calking a large water pipe. 



Wgr~>^ 




-riveting with the balance attachment. 



THE WORK OF PNEUMATIC TOOLS. 



477 





478 COMPRESSED AIR AND ITS APPLICATIONS. 




FIG. 286.— LONG-STROKE HAMMER AND HOLD-ON IN STRUCTURAL WORK. 



PNEUMATIC TOOLS. 



479 




COMPRESSED AIR DRILLS AND THEIR WORK. 

The simple rotary air drill for hand use commends itself as 
one among the handy tools of a shop. It may consist of a 
rotary air motor fixed to the drill spindle, in a case to which 
the handles and breastplate are attached. Compressed air en- 
ters through the handle with the valve lever and is exhausted 
through the opposite handle. 

Another form of rotary air motor drill stock, with simple 
blades held to the cylinder and central over the drill spindle, 
is illustrated on page 488. 
The motor journals termi 
nate in a small bevel pinion 
that meshes in a ring gear 
attached by the lower sec- 
tion of the case to the drill 
spindle, the handles being 
attached to the upper or 
motor section of the case. 

In Fig. 287 is shown the vertical section of an oscillating 
piston drill, in which one of the cylinders and trunnions is 
shown at the right, in the trunnions of which are placed the 
inlet and exhaust port. The air enters the revolving central 
spindle through the small holes shown in the hollow spindle 
and is delivered to the oscillating trunnion through the lower 
hole in the hollow part of the spindle. 

In Fig. 288 are represented the outside view, the horizontal 
section, and the vertical section of a Haesler pneumatic drill. 
It is operated by four pistons in two cylinders, double-acting. 
The piston rods have a jointed connection to cam cranks on the 
pinion shafts. The piston valves are operated by levers pivoted 
to opposite piston rods, as shown in the horizontal section. 
The pistons act alternately in the cylinders so that there is no 
dead centre. The large spur wheel is attached to the spindle 
and revolves with it. 



Fig. 287.— vertical section. 



480 



COMPRESSED AIR AND ITS APPLICATIONS. 




THE HAESLER DRILL. 



In Fig. 289 are shown a 
vertical view and a sectional 
plan of a three-cylinder os- 
cillating motor drill. The 
compressed air enters 
through one of the handles, 
its flow being controlled by 
a lever and valve. The ex- 
haust enters the case from 
the port in the oscillating 
cylinder trunnions. The 
three double-acting pistons 
are directly connected to 
cranks and pinions which 
mesh with an internal spur 
gear, which is fast to the 
outer shell. The spider 
which carries the cylinders and pinions is fast on the central 
spindle and revolves with it. The inlet and exhaust ports 
are shown in the horizontal section of the top trunnion at A. 

In the succeeding illus- 
trations are shown some of 
the standard types of pneu- 
matic drills. Fig. 290 is a 
longitudinal sectional eleva- 
tion of a " Little Giant " port- 
able air drill, taken on the 
central line 1 — 1 of the hori- 
zontal section (Fig. 291). 

In this type of drill the 
motor consists of four single- 
acting cylinders arranged in 
pairs, and having each pair 
of pistons connected to op- 
posite ends of a double FlG . 289 ._ THE PISTON DR i LL . 




PNEUMATIC TOOLS. 



481 




Fig. 290.— little giant, sectional elevation. 



crank-shaft. The pistons of each pair travel in opposite direc- 
tions at all parts of the stroke to effect smooth running. The 

cylinders are controlled by 
balanced piston valves set to 
cut off at five-eighths of 
the stroke, and should there- 
fore prove economical. Re- 
ferring to Figs. 290 and 
291, A is the main casing, 
which contains the mechan- 
ism ; B and B ' are one pair 
of cylinders, and C and C 1 
are the other, arranged at 
right angles to each other 
and connected to a common 
crank shaft D. By this ar- 
rangement a dead centre is avoided. The air admission and 
exhaust are controlled by two piston valves, E and E\ These 
are worked by small eccentrics off the crank shaft, and serve 
to control the four cylinders ; /is the main pressure chamber, 
having communication with 
the supply pipe H. The 
arrows show the direction 
taken by the air. Cylinders 
B and B ' receive air com- 
munication through f 2 and 
f s , and cylinders B and B 1 
through c 3 and c\ the exhaust 
taking place through the in- 
terior of the two valves. 
The action is as follows: / 
is full of live air which is 

blowing through c* and/ 3 , to supply cylinders C and C\ while 
cylinders B and B 1 are exhausting through / 2 and c* into the 
centre of the valves, and thus to the atmosphere. Referring to 
31 



I - 




little giant, section through 
cylinders. . 



482 



COMPRESSED AIR AND ITS APPLICATIONS. 




Pig. 292.— little giant, high speed. 



Fig. 290, k and k l are gear wheels by which the rotary motion 
of the crank-shaft is conveyed to the part K, which is fitted 

with a suitable drill-holder or 
chuck. L is a threaded 
sleeve, which, in conjunction 
with L 1 and other parts, pro- 
vides for feeding the drill. 
This tool is also furnished 
with a simple reversing ar- 
rangement, which enables it 
to do all classes of work for which a drill is suitable ; for this 
it is fitted with a handle in the place of the star centre. By 
revolving this handle a valve placed in the main pressure 
chamber reverses the direction taken by the air when entering 
the valve bushing, suitable ports being provided. 

Figs. 292 and 293 illustrate the " Little Giant " high-speed 
rotary drill, which consists of a casing C containing three rotat- 
ing cylinders F, each of which is governed by a piston slide 
valve E. These valves rotate with and work in cylinders or 
valve chambers forming part of the main engine cylinders F. 
In other machines for effecting the same and similar purposes 




Fig. 2oq,— little giant fixed cylinders. 



the casing is used as a live-air chamber; in the " Little Giant " 
type it is used as an exhaust receiver. Again, in other 
machines the air is directly admitted into the casing C or 



PNEUMATIC. TOOLS. 483 

live-air chamber, whereas with the " Little Giant " drill it is 
carried through a separate channel from the supply pipe A, 
and through a stationary or fixed hollow crank-shaft B, into a 
passage L, leading to the reduced portions of the piston slide 
valves E, and according to the position of such valves admitted 
to, or exhausted from, the cylinders F. It will also be noticed 
that in the " Little Giant " 
drill the exhaust does not 
blow through the gear 
mechanism, since it is so 
arranged that it is admit- 
ted into the main casing C, 
which is itself sealed from 
the lower portion of the 
machine, containing the 
reducing gear, so that the 
exhaust passes out through 
a separate pipe K. 

The leading feature in 
the " Little Giant " machine 
is that it combines a high- 
speed engine with a low 
consumption of air, and 
this result has been ob- 
tained by employing a stationary eccentric, which is set at the 
required point in the throw of the crank to obtain the neces- 
sary cut-off, the cylinders F, and their governing slide valves E, 
rotating about this eccentric. As is well known, in engines of 
this type the travel of the eccentric should be quickest when 
the motion of the piston is slowest, and this is provided for in 
the design by having a very quick port opening and an equally 
quick release, thus enabling the rotating cylinders to move at 
an exceedingly rapid rate, the air not having to travel through 
tortuous passages either in or out. 

Fig. 294 illustrates a transverse vertical section of a 




Fig. 294.— section, boyer drill. 



4§4 



COMPRESSED AIR AND ITS APPLICATIONS. 



" Boyer " piston drill, and Fig. 295 is a horizontal section taken 
through the centre of the cylinders. The machine consists of 
three main parts : (1) The upper housing into which the 
throttle valve and steadying handle are screwed, and which 
forms a live-air chamber carrying the motor; (2) the diaphragm 
which forms the lid or cover of the upper housing or live-air 
chamber, and through which the hollow exhaust spindle pro- 
jects ; (3) the lower housing secured to the upper housing by 
means of screws, and containing the gear-wheel rack bearings 
for drill spindle, etc. The motor is in the form of a three- 
cylinder single-acting oscillating engine, the cylinders being 

carried in the rotary frame. 
This frame consists of an up- 
per and a lower plate, and is tri- 
angular in shape and free to 
revolve round its centre on two 
bearings, the lower one being 
a hollow shaft, connected by 
gearing to an internally toothed 
wheel in the lower half of the 
casing. The admission of air 
to the cylinders is regulated by the valves formed in the pivots 
upon which the cylinders oscillate. The cylinders are single 
acting, and the inner ends are open ; therefore air under press- 
ure, of which the upper casing is always full, has free ac- 
cess to the pistons on that side. It would seem, therefore, 
that air being admitted through the pivot valves would only 
produce equilibrium ; but since one of the cylinders is always 
open to the exhaust through the hollow bearing of the triangu- 
lar frame, this equilibrium becomes disturbed, and the com- 
pressed air has full effect upon each piston as the valve comes 
in line with the exhaust. The cylinders are constructed of 
steel tubes, and are fitted with trunk pistons having their con- 
necting-rod ends attached to a fixed crank-pin common to them 
all. The pistons are set in motion by the introduction of 




HORIZONTAL SKCI !<>N, HOVER. 



PNEUMATIC TOOLS. 



485 



compressed air into the tipper casing and into the cylinder as 
already described ; this has the effect of causing the three cylin- 
ders, together with their triangular framing, to rotate round 
the fixed crank pin, and thus transmits rotary motion to the 
spindle by means of the gearing before referred to. This class 




Fig. 296.— the vvhitelaw drill. 



of machine is fitted with a regulator by means of which the 
power and speed of the drill can be varied as desired. 

Fig. 296 shows the interior of a " Whitelaw " reversible drill 
with half the casing removed, showing the piston valve / and 
the passage of the air leading to the cylinder and the method 
of reversal. This type of drill is actuated by two double-acting 



486 COMPRESSED AIR AND ITS APPLICATIONS. 

oscillating cylinders A and B, driving a crank shaft C, to which 
is attached a pinion D driving the gear wheel E, attached to 
the drill spindle. Its action is therefore at once apparent; 
for by rotating the milled handle E, which gears into the 
short rack G at the end of the lever H, the hollow portion of 
the piston valve /changes its position, with the result that re- 
versal takes place in the usual way adopted in oscillating cylin- 
ders. The exhaust is made into the casing and escapes through 
suitable apertures. The reversal is instantaneous, and the 
machine is well adapted for all kinds of drilling, tapping, tube- 





y 



Pig. 297.— the boyer piston air drill. 

expanding, wood-boring, etc., the reversing arrangement espe- 
cially lending itself to such purposes. The machine is sup- 
plied with ample lubrication, and is fitted with ball bearings 
throughout. 

The Boyer piston air drill is of the three-piston type, and is 
adapted for drilling iron and steel up to three inches in diameter 
(Fig. 297). It is used extensively in boiler shops, shipbuilding 
concerns, machine shops, architectural works, foundries, etc. 
Many appliances are used in connection with these drills, such 
as flue rollers, grinding-chucks, flue cutters, stay-bolt cutters, 
and side-light cutters. 

Fig. 298 shows the method of driving countersunk flush 
rivets on the bottom of a vessel by compressed air. The small 



PNEUMATIC TOOLS. 



487 



hammer seen in the illustration is used for chipping the head 
of the rivet smooth, and the drill is used to ream the rivet holes 
to a sufficient diameter to receive the rivet. 

The pneumatic rotary motor drill stock consists of a hori- 
zontal rotary motor, over the centre of the spindle, having on 
one end of its shaft a bevel pinion, which drives a bevel gear 




.—THE PNEUMATIC DRILL AND HAMMER IN SHIP WORK. 



attached by the lower section of the case to the drill spindle. 
The inlet and exhaust ports and valves are shown in the verti- 
cal section. 

The rotary drill, as shown in Figs. 300-302, is the early 
type of pneumatic drill, and is still extensively used on heavy 
drilling and reaming. Its simplicity of construction and small 
number of working parts give it some advantages over the more 
complicated types of air drills. 



COMPRESSED AIR AND ITS APPLICATIONS. 




Fig. 299.— the phgenix rotary air drill. 




PIG. 300.-ROTARY BREAST DRILL. FlG. 301.— THE ROTARY. FlG. 302 —SECTION. 



SU-. 



L 




FlG. 303.— THE light breast'drill. 



PNEUMATIC TOOLS. 489 

The Chicago breast drill is of the oscillating cylinder type, 
and is capable of drilling up to \ inch in iron or steel. It is 
an invaluable tool where a large number of small holes are to 
be bored. It is used for wood-boring with equal success. 

« Fig. 303 is an illustration of the Chicago rotary breast 
drill, a very light, compact drill capable of drilling up to f inch 
in metal. 

Fig. 304 is a larger-sized drill of the same type as in the pre- 
ceding illustration, and is adapted for drilling up to -^ inch in 




Fig. 304.— the medium breast drill. 
Weight, five pounds. 

metal, and also for light wood-boring. It can be used with feed 
screw. It is employed in shops having a lighter grade of work 
both in iron and brass ; also in wood-working establishments, 
in the building of small wooden vessels, where a great number 
of small holes are to be bored. 

The Whitelaw types of reversible drills are for all kinds of 
wood-boring. They are used extensively in car shops, wood 
shipyards, etc. ; are very light, and will bore up to four inches 
diameter in about one-fifth the time required by hand methods. 



49° 



COMPRESSED AIR AND ITS APPLICATIONS. 




Fig. 305.— the Chicago breast drill. 



PNEUMATIC TOOLS. 



491 




FIG. 306. — WHITELAW REVERSIBLE DRILL. 




FIG. 307.— WHITELAW REVERSIBLE WOOD-BORING DRILL. 

Weighs ten pounds, and will bore up to four inches diameter. 



492 



COMPRESSED AIR AND ITS APPLICATIONS. 




$ "3 




THE WORK OF PNEUMATIC TOOLS. 



493 




I 




a o 



494 



COMPRESSED AIR AND ITS APPLICATIONS. 





WW : 

6 > 








THE WORK OF PNEUMATIC TOOLS. 



495 





496 COMPRESSED AIR AND ITS APPLICATIONS. 




Fig. ^16.— drilling and riveting with pneumatic tools. 




Fig. 317.— drilling manhole in a tank. 



Chapter XXIV. 



PNEUMATIC TOOLS— Continued 



PNEUMATIC TOOLS. 

(Con tin tied.) 

PNEUMATIC HAMMERS OF THE Q. & C. COMPANY, 
NEW YORK CITY. 

The hammers of this company are made in four sizes, and 
are used with pressures of from 80 to 90 pounds for their best 
work. Fig. 318 shows this hammer in section, consisting of a 
differential cylinder case containing the air passages for press- 




FlG. 318.— SECTION OF THE Q. & C. HAMMER. 

ure and return stroke, and the relief chamber and exhaust 
port. In the handle the spring-closed air valve and thumb 
lever are plainly shown. The piston has a differential action in 
which the annular chamber due to its enlarged upper section 
allows the up-stroke to be made with a small piston area sub- 
ject to pressure, and a much greater area on the down-stroke for 
its greater work. The piston has a hollow centre leading to a 
side port, which exhausts the down-air pressure at the moment 
of closing the inlet port and simultaneous with its impact with 



500 COMPRESSED AIR AND ITS APPLICATIONS. 

the tool or chisel. The piston is returned by the pressure in 
the annular section. 

In Fig. 319 is shown a lettered section of the Q. & C. 
pneumatic hammer, the basis of construction of which is the 
Johnson patent. The small globular chamber A, together with 
the conical chamber in the piston, is charged with compressed 
air at the moment the air port 5 reaches the inlet space Po, 
when the elasticity of the air in the chamber carries the piston 
forward, closing the inlet port and pushing the piston to its 
stroke, when the air is exhausted at the chamber and port E. 
Fis the flexible hose connection, and T the air-valve trip. The 




Fig. 319.— section of q. & c. hammer. 

air enters in the direction of the arrows in the cut and into the 
annular section of the cylinder and piston, lifting the piston 
to the top position of the stroke, when the piston ports open to 
the annular chamber and the full air pressure is thrown against 
the piston. 

The diameters of the four smaller sizes of pistons are respec- 
tively 1^ and \\ inches; stroke, \, 1, and 2 inches; weight, ^, 
f, 1, 1^ pounds, making from 1,500 to 2,500 strokes per minute. 
From the known weight of the piston, length of stroke, and 
number of strokes made per minute, the force of the hammer 
blow may be computed by formulas given on another page. 

Although these hammers, with their smaller-sized pistons, 
when compared with a machinist's hammer or the mallet of the 
stone-cutter, seem very light for effective work, yet their light 
weight is in a great measure compensated for by their velocity 



PNEUMATIC TOOLS. 



50I 



of about 30 feet per second at the moment of impact. This ve- 
locity, with a pressure of from 50 to 100 pounds behind it, pro- 
duces a result that is fully equivalent to the ordinary blow from 
a much heavier hand-hammer. 

Fig. 320 shows the manner of holding the hammer and 
chisel in chipping plate work. Fig. 32 1 is a stone-carving ham- 
mer, the form of which is 
required to adapt its posi- 
tion quickly to variable 
surfaces. It is held by the 
cylinder in one hand with 
the thumb on the knurled 
adjusting screw, while the 
other hand guides the 
chisel. 

Riveters with yoke 
frames of various dimen- 
sions, and fitted with pneu- 
matic hold-on, have many 
advantages when provid- 
ed with claw compressors 
around the riveting ham- 
mer to hold the rivet-head hard against the plate and to keep 
the plates tight together by pressure of the piston of the hold- 
on. The claw is seen in the cut at the right around the ham- 
mer, Fig. 322. 

When the riveter is placed over a rivet, the air valve at the 
left in the cut is opened, and air pressure, which may be 200 or 
more pounds according to the area of the piston, pushes the 
head of the rivet and the plates tight against the hammer claw; 
then by opening the valve at the right-hand side, the hammer 
is operated with the full force of the air pressure. 

Fig. 323 shows the method of suspending a yoke riveter for 
a free set in any angular position. The point of suspension is 
at the centre of gravity, so that the riveter is easily held in any 




Fig. 320.— chipping. 



502 COMPRESSED AIR AND ITS APPLICATIONS. 




Fig. 321.— stone-carving hammer. 




Fig. 322.— yoke riveter. 



PNEUMATIC TOOLS. 



503 



desired position. In this type the cylinder of the striking 
hammer is advanced to catch the end of the rivet by sliding 
forward in the outer shell at the same moment that the ham- 




PlG. 323.— YOKE-RIVETER SUSPENSION. 

mer begins to operate, and is held there by the same pressure 
that operates the hammer. 

The bar-yoke riveter may be suspended for vertical work; 
it being a universal suspension arrangement by which any 
position may be obtained by a mere change in the socket hold. 
This class of riveters above 30-inch gap are made with pipe 
frames up to 6 or more feet gap, with varying openings from 
10 to 14 inches, or more if desired. 



504 COMPRESSED AIR AND ITS APPLICATIONS. 




Fig. 324.— section of moving parts of yoke kivetek. 
The cushion hold-on. 




Fig. 325.— section of solid head and moving parts of yoke kiveter (q. & c. co.) 



PNEUMATIC TOOLS. 



505 




d ^ 1 



Fig. 326.— stationary riveter. 




teg 




Fig. 327. -piston pneumatic drill. 



506 



COMPRESSED AIR AND ITS APPLICATIONS. 



In Fig. 326 is represented a stationary riveter with a differ- 
ential piston which closes upon the plates and rivet-head with 
great pressure, when the hammer piston finishes the work of 
riveting. The three-way valve at the left above the cylinder 
gives full air pressure at the back of the push piston and oper- 
ates the hammer piston. By its reversion it becomes the ex- 
haust port, and by opening 
the right-hand valve the 
push piston is withdrawn. 

The pneumatic drills of 
the Q. & C. Company are 
illustrated in Fig. 327, 
showing the construction, 
which consists of four pis- 
tons, single-acting, con- 
nected in pairs to two 
crank shafts with pinions, 
meshed in a larger driven 
gear, which carries the 
drill. Each crank shaft 
operates piston valves to its 
pair of cylinders and is set 
at three-fourths cut-off. The air inlet is regulated by twisting 
the sleeve on the hose handle, called a rotary throttle. Two 
sizes are made, of 40 and 28 pounds weight, which will drill 
holes of 2\ and \\ inches respective^. 

Fig. 328 represents the reversible drill of the Q. & C. Com- 
pany, for wood-boring and light metal work. It is of the same 
general construction as their heavier drills, but is valveless, as 
the pistons control the air passages. There are two spindles 
for high and low speeds, and by means of a special chuck the 
tool can be quickly changed from one spindle to the other. 
The drill is reversed by a small lever separate from the handle. 
The handle at the top can be replaced by a breastplate or a 
feed-screw, shown in the illustration. 




Fig. 3 



DRILL AT WORK. 



PNEUMATIC TOOLS. 507 



PNEUMATIC TOOLS OF THE STANDARD RAILWAY EQUIPMENT 
COMPANY, ST. LOUIS, MO. — HAMMERS. 

The "AA" Monarch hammer has a i-inch diameter piston. 
The stroke is also 1 inch, and the hammer runs at an estimated 
speed of 2,800 strokes per minute. Weighs 9I pounds and is 
best. adapted for light calking and chipping. 

The "A" Monarch hammer has a i-inch diameter piston, 
the stroke is if inches; this hammer runs at an estimated speed 
of 2,300 strokes per minute. Weighs 10-i- pounds, and is espe- 
cially desirable for general use in boiler shops and foundries, 
for chipping iron and steel, calking on boilers, and beading 
flues. 

The "B" Monarch hammer has a i-inch diameter piston, 
and the stroke is 2\ inches ; it runs at an estimated speed of 
2,000 strokes per minute. Weighs 12 pounds. It is best 
adapted for heavy chipping, such as steel castings, boiler 
plates, and light riveting. 

The consumption of air for these tools is from 15 to 18 cubic 
feet of free air per minute, and they operate best at a working 
pressure of from 80 to 100 pounds. 

Their hammers are provided with a regulating valve, which 
enables one to use a large hammer for the lightest kind of chip- 
ping, as well as for very heavy chipping. 

Great care should be taken that the working parts are kept 
free from grit and dirt, and the tools be kept well lubricated 
with a good grade of light oil. 



Their iron drills and wood-boring machines are all three- 
cylinder machines. The cylinders oscillate on one valve. The 
cranks have roller bearings throughout; except the spindles, 
which have ball-bearings. The pistons are provided with roller 



508 



COMPRESSED AIR AND ITS APPLICATIONS. 




Fig. 329— the monarch long-stroke riveter. 



n 





Q 



mmM 

-a 



PNEUMATIC TOOLS. 509 

bearings where they connect to the crank, which is a solid 
three-point crank made of tool steel, and hardened for the roller 
bearings. They use cut gears; the pinions are made of tool 
steel and hardened. The wood-boring machines are made re- 
versible, the reversing throttle and starting throttle being in 
one piece and also forming part of the hose connection. The 
Monarch drill No. 4, which is a combination drill, and can be 
used for either wood-boring or iron-drilling, can be made re- 
versible by sliding a small screw on the throttle valve. This 




Hi 
Fig. 331.— monakch piston air drill no. i. 

drill is especially desirable for expanding flues and for tapping 
purposes. 

The No. 1 Monarch drill has a capacity for drilling and 
reaming up to 2\ inches in diameter in any kind of metal, and 
is economical in the consumption of air, only consuming about 
20 cubic feet of free air per minute ; it weighs but 32 pounds, 
and runs about 250 revolutions per minute. It can be used 
within three inches of a corner, and measures 14 inches from 
end of feed screw to end of spindle. All the gears and working 
parts are well protected from dirt, and all moving parts can be 
oiled while machine is running. 

The Monarch No. 4 drill is built on the same principle as 
all of this company's drills, having three cylinders with a solid 



5io 



COMPRESSED AIR AND ITS APPLICATIONS. 



three-way crank made of tool steel, to which the three pistons 
are attached, with roller bearings in each crank connection. 

This machine will drill a hole up to \\ inches in any kind 
of metal; it makes about 375 revolutions per minute, consum- 
ing about 18 cubic feet of free air per minute. It weighs 20 
pounds, and is arranged so that it can be made reversible by 
simply pushing a small button in or out on the throttle valve. 
This drill is especially desirable for stay-bolt tapping, reaming, 




Fig. 332.— monarch drill no. 4. 

expanding flues, and for various other purposes. By taking 
the feed screws off and substituting a handle it can be used as 
a wood-boring machine. 

PNEUMATIC TOOLS OF THE PHILADELPHIA PNEUMATIC TOOL 
COMPANY, PHILADELPHIA, PA. 

The pneumatic hammers of this company are made in four 
sizes, of 8, 9, ioi-, and 12 pounds weight, for riveting, chipping, 
and calking. They are made on the constructive lines of the 
"Little Giant," detailed on other pages of this work. Air re- 
quired per minute according to size, from 10 to 14 cubic feet. 

The pneumatic hold-on has an air piston and die which is 
held to the rivet with the force of the air pressure due to the 
area of the piston. The length of the cylinder and die is 12 
inches, length of stroke 3§ inches. 



PNEUMATIC TOOLS. 



511 



Chipping by the pneumatic hammer and chisel is vastly 
ahead of the power of human muscle for effective work. Our 
illustration (Fig. 335) shows what can be done with a No. 3 




FlG. 333. — THE RIVETING HAMMER. 

hammer and chisel in rolling up the chips on a strip of -|-inch 
boiler plate at the rate of 1 foot per minute, using air at 80 
pounds pressure per square inch. 

Chipping of any kind, whether on wrought or cast iron, steel, 
or even the softer metals, is a drag life to the mechanic, who 
can find relief from the irksome task only by stopping the slow 
and tedious work to rest his weary muscles ; but when he can 




Fig. 334.— pneumatic hold-on. 

roll off ai big chip at the rate of a foot a minute by air power, 
the mechanic art becomes a pleasant pastime. 

We illustrate in Figs. 336 to 338 the foundry air tools of 
the Philadelphia Pneumatic Tool Company : the light sand ram- 
mer operated by an ordinary pneumatic hammer, a special 



512 COMPRESSED AIR AND ITS APPLICATIONS. 



r ;— 














-^^ / r 






Wt jt'^XS 








, / 


S.j '.'.'.'•!: ...: 





Fig. 335.— fast chipping. 



double-handle rammer, and an adjustable rammer for suspen- 
sion from a crane. 

Power rammers for heavy work in foundries are compara- 
tively recent innovations, and from their simple construction 
and the enormous amount of work that they will accomplish 
they are being rapidly adopted in this country and in Europe. 





Fig. 336.— light rammer. 



Fig. 337.— two-handle rammer. 



PNEUMATIC TOOLS. 



513 



By the use of these machines one man 
can readily do the work of from eight to 
twelve men. All he has to do is to direct 
the blows of the rammer, moving the ma- 
chine about over the work by means of 
the handles. 

These rammers use air at a pressure 
of about 80 pounds per square inch, and 
strike from 250 to 300 blows per minute. 
The air supply is absolutely under the 
control of the operator, and he can thus 
regulate the force of the blow to the 
utmost nicety, and start and stop the ram- 
mer at will. 

The light pneumatic rammer is simi- 
lar in construction to the heavier type of 
pneumatic rammers, but still is light 
enough to be easily handled by the oper- 
ator. It is at the same time sufficiently 
heavy for its inertia to absorb any vi- 
bration that may arise from the rapid 
reciprocation of its piston and rammer 
head. The valve mechanism and parts 
are as simple as is consistent with smooth 
working, and are suitably enclosed and 
therefore free from dust and dirt. The 
rammer head is a hexagon and can be 
turned at the will of the operator. The 
weight of this tool is 45 pounds, and it 
strikes 250 to 300 blows per minute, with 
an air pressure of 50 to 100 pounds per 
square inch, only 15 cubic feet of free air 
per minute being used when in contin- 
uous operation. The air is admitted to 
the handle on the right side, its admission 
33 



338.— SUSPENDED RAM- 
MER. 



5 14 COMPRESSED AIR AND ITS APPLICATIONS. 

being controlled by a throttle lever under the thumb of the 
user; the exhaust passes through the handle on the left. 
Speed and force of the blow can be varied at will. A number 
of different-shaped heads are provided with each machine. 
These are attached to the rammer rod by means of a taper fit, 
and may be changed in less than half a minute and without 
letting go of the handle. 

The constructive features of the hammers and rammers of 
this company are based on the Keller patents. 

THE COUNTERBALANCED SAND-RAMMER IN FOUNDRY WORK. 

In Fig. 338 is represented one of the modern adjuncts of a 
foundry for the saving of the severe labor of ramming large 
moulds. This sand-rammer is accurately counterbalanced and 
weighs with its complete rig nearly 300 pounds. It is oper- 
ated by air pressure of about 40 pounds per square inch, and 
will deliver 300 blows per minute. 

The maximum stroke is 7 inches, and the intensity and 
length of stroke may be varied at the will of the moulder by 
simply altering the distance of the rammer from the sand. 

THE PNEUMATIC SAND-SIFTER. 

The meagre mechanism of the foundry has lately received 
an important addition in the machine illustrated in Fig. 339. 
It is a sand-sifting machine, operated by compressed air. 
It consists of a heavy oak frame, containing a swinging rid- 
dle or sieve, that can be removed by simply lifting it out of the 
frame when necessary to use a sieve of different mesh. The 
motive power is a substantial balanced rotary motor of the Chi- 
cago Pneumatic Tool Company, which drives the gear connected 
to the three-pointed knocker attached to the sieve. Foundries 
which are using these machines state that they not only cover 
their cost in a short while by economy in labor, but that the 
tempering of the sand can be done much better than by hand. 



PNEUMATIC TOOLS. 



515 



One of the numerous special employments of compressed air 
in foundry work is the revolving steel brush for cleaning cast- 
ings, operated by a rotary air motor. It finds many places for. 




Fig. 339.— pneumatic sand-siftek. 

useful work where the sand blast is not available, especially for 
inside cleaning after cores and moulding sand have been re- 
moved. These, with the many other applications of special air- 
driven tools noted in this work, suggest the inevitable conclusion 
that, when once you have compressed air available, the number 






Fig. 340.— pneumatic casting cleaner. 



of convenient and economical possibilities that it presents to 
the progressive operator is surprising, and its field of service 
broadens with amazing and gratifying rapidity. 



516 



COMPRESSED AIR AND ITS APPLICATIONS. 



THE MOULDING MACHINE IN THE FOUNDRY. 

One of the best labor-savers in the foundry is the pneumatic 
moulding machine. The early forms of small flask moulding 
machine required shafting, belts, and gears to operate them, 
which are not always convenient in a foundry moulding-room. 
The pneumatic system requires only a compressed-air pipe 
from the source of compressed-air supply in the main works 

with connections, when the 
machine is ready for work. 
The machine is constructed 
on the lines of a hydraulic 
lift, except that the pressure 
piston is operated by direct 
air pressure of from 75 to 80 
pounds, as used in the oper- 
ation of other pneumatic 
machines and in machine 
and constructive works. 
The upper platen is adjusted 
and fixed in its working position by tie rods jointed at the bot- 
tom of the machine, by which it can be moved off from over the 
flask for filling with sand, and removing patterns and flask. 
The lower platen carrying the flask moves upward by the air 
pressure in the cylinder and compresses the sand by a weight 
equal to several thousand pounds, merely by turning a three- 
way cock as shown at the right-hand side of the cut. After 
ramming, the head is pushed back, and the match and drag 
are turned over in the usual way. The match is then removed 
and the cope flask is fitted over the pins ; parting and moulding 
sand is then filled into the cope and put under pressure. A 
pneumatic vibrator, made on the lines of the vibrating piston 
in a pneumatic hammer, is attached to the flask, by which a 
sharp tremor is set up in the vibrating frame and patterns, when 
the cope and patterns may be drawn in the usual way. 




Fig. 341.— pneumatic mouldi: 



PNEUMATIC TOOLS. 



517 



The pneumatic moulding machines are made in several sizes 
by the Tabor Manufacturing Company, Philadelphia, Pa. 



THE FLUE-WELDING HAMMER. 



A most important adjunct of the locomotive shop. It is used 
for piecing out and welding out tubes which have been damaged 
by the burning of end or by removal. 




Fig. 342.— the pneumatic flue-welding machine. 
Chicago Pneumatic Tool Company, Chicago, 111. 



A PNEUMATIC ROCK DRILL AS A HAMMER. 

This consists essentially of a drill mounted in a forged steel 
frame, which is suspended by the arms (shown in Fig. 343) to a 
frame with holding brackets ; making a rig that can be handled 
with ease, and doing the work required in less time and at a 
lower cost than has been done heretofore by hand. 



5 l8 COMPRESSED AIR AND ITS APPLICATIONS. 

It has been used extensively in the construction work on the 
piers for the new East River Bridge, for driving drift bolts. A 
record of its performance there has been kept, establishing there- 
by another and permanent use for rock drills in a new field. 
Is is a large type of the pneumatic hammer. It is the Little 

Giant drill of the Rand 
Drill Company. 

COMPRESSED-AIR DRILLS OF 
THE PHILADELPHIA 
PNEUMATIC TOOL COM- 
PANY. 

These are of the rotary 
type specified in the gen- 
eral description on another 
page, and are made in two 
sizes, weighing 45 and 58 
pounds, and using 35 cubic 
feet of air per minute for 
full service. The small 
size will drill a i|--inch hole 
in steel, while the larger 
size has a capacity of 
drilling a 3-inch hole in steel, with 80 pounds air pressure. It 
is a powerful all-round machine for drilling, reaming, tapping, 
and stay-bolt screwing. The motor blades are fitted with 
metallic packing which automatically takes up wear and main- 
tains efficiency of the working parts. 

AIR DRILLS OF THE STOW FLEXIBLE SHAFT CO. 

In Fig. 345 is illustrated the rotary motor drill made on the 
lines of the patent of Caid H. Peck, No. 507,752, consisting of 
a rotary motor revolving on the drill spindle and reducing its 
speed motion to the spindle through a set of differential gears. 




Fig. 343.— pneumatic drift-bolt driver. 



AIR MOTOR DRILLS. 



519 




FIG. 3.44.— PNEUMATIC ROTARY DRILL. 




FIG. 345.— AIR DRILLS OF THE STOW FLEXIBLE SHAFT COMPANY, PHILADELPHIA, PA. 



520 



COMPRESSED AIR AND ITS APPLICATIONS. 



Air is admitted through one handle by the lift of the valve 
lever, into the inside of the piston, and is forced out through 
holes directly against the vanes ; this starts the piston to re- 
volving, and when it gets around to the other handle this air 
has done its work and is exhausted. 

The motion of the piston is transmitted through the double 
sun-and-planet gears in the gear case to the spindle, and the 
speed of this spindle is regulated by the number of gears. In 
what is called the single-geared machine, as illustrated in the 
right-hand figure of the cut, the speed is reduced to one degree, 




■*? 




Fig. 346.— air motor operating a drill with a stow flexible shaft. 



while in the double-geared machine there is a second set of 
gears, and the speed is only half as great. 

The air motor is composed of a pair of cylinders, oscillating 
on centres, taking air from a cylindrically faced air chest, 
through suitable passages and ports, and giving motion to the 
crank shaft. This is the strong point of the machine; it is 
made from the solid forged steel, and will stand all the work 
that can be put on it safely. The normal speed of about 1,200 
revolutions is reduced by a set of speed-reducing gears in the 
case at one end, and the other end has a small balance-wheel and 
a lever for starting or for slowly working by hand if necessary. 



AIR MOTOR DRILLS AND HOISTS. 



521 



AIR DRILLS AND HOISTS OF THE EMPIRE ENGINE AND MOTOR 
COMPANY, ORANGEBURG, NEW YORK. 

The drills of this company are made in five sizes, having a 
capacity for drilling in metal from T 3 ¥ to i-i-inch holes. They 
are driven by a horizontal ro- 
tary motor with a pinion mesh- 
ing into two intermediate 
gears, and they into an inter- 
nal gear rack, which is sta- 
tionary, being held in place 
by the cylinder head. The 
two intermediate gears are 
placed radially on the arms of 
the spindle, which travels 
with the gears, thereby equal- 
izing the strain on bearings 
and making friction light. 

The air-motor hoists of 
this company are illustrated in 
Figs. 349 and 350. They are operated by a rotary motor con- 
taining two blades in an eccentrically located piston as shown 




FlG.347.— BREAST DRILL. 




Fig. 348.— the rotary movement. 



522 



COMPRESSED AIR AND ITS APPLICATIONS. 





PNEUMATIC HAMMERS. 



523 



in the detailed cut, and geared by double pinions to large gear 
wheels with differential chain sheaves on the main shaft. 
They do not depend upon air pressure to sustain the load, 
being provided with a brake. They are also made to run on a 
suspended trolley or boom of a jib crane. 

PNEUMATIC TOOLS OF THE C. H. SHAW PNEUMATIC TOOL 
COMPANY, DENVER, COLO. 

The tools are very simple in their construction, yet efficient 
for work. The chipping and calking hammer is made up of six 




-THE ECLIPSE HAMMER. 



pieces and is so simple in form that any machinist can renew 
the parts liable to wear. It has a spring handle and is valve- 
less in the operating parts, the admission air valve being oper- 
ated by the grasp of the handle. 

The marble- cutter's hammer is equally simple in construc- 
tion ; it has a compression air valve operated by the pressure of 




Fig. 352.— parts of the eclipse hammer. 



524 



COMPRESSED AIR AND ITS APPLICATIONS. 



the thumb, and also a screw regulating valve to regulate the 
air pressure for very light work. Usual air pressure, 30 to 50 
pounds for marble work. 

The two-cylinder compound air drill of this company is illus- 
trated in Fig. 354. The arrangement of the pistons and 




Fig. 353.— the marble cutter's hammer. 

connections is such as to allow of no dead centre, and the com- 
pounding of the cylinders carries the exhaust nearly to atmos- 
pheric pressure. A more powerful drill, having four cylinders, 
is manufactured by the same firm. This company also makes a 
single-cylinder rotary drill or tapping machine with a four- 
bladed piston having no dead centre or weak place in its revo- 




FlG. 354.— COMPOUND AIR DRILL. 



PNEUMATIC HAMMERS. 525 

lution. It is made in two sizes, for drilling and tapping, up to 
iland ii-inch holes respectively, and is very suitable for boiler 
work. 

PNEUMATIC TOOLS OF THE AMERICAN PNEUMATIC TOOL 
COMPANY, NEW YORK CITY. 

The tools of this company have been long in use for metal 
and stone work, and are simple in design and effective in their 




FlG - 355.— PNEUMATIC HAMMERS OF THE AMERICAN PNEUMATIC TOOL COMPANY. 



working power. They are made in three sizes, for light, me- 
dium, and heavy work. 

The details of the parts of these hammers are as follows : 
the handle and valve-seat case screwed upon the cylinder, the 
valve block or seat containing the air passages, and the valve 
spool which operates automatically in the valve block, the pis- 
ton, and tool bushing. 



526 



COMPRESSED AIR AND ITS APPLICATIONS. 



The stone-dressing pneumatic tools of this Company are 
here illustrated in four sizes, of which the A size is a very light 
tool for tracing and small lettering ; the BX size is for heavy 
lettering and carving, and the other two are for heavier cutting 
and roughing. 

The lighter tools are for lettering and finishing. In this 
class the piston contains the automatic valve, and part of the 




Fig. 356.— stone-dressing pneumatic hammers. 

exhaust opens at the nose of the tool to blow away the chips 
and dust. 

The detailed parts are shown in Fig. 357. 1 is the cylinder 
screwed to the nose-piece 7, and covered by a jacket 4. The 
piston 5 is perforated across the centre and contains the spool 
valve and internal ports and air passages for operating the pis- 
ton, their counterpart being through the walls of the cylinder, 
communicating with the inlet and exhaust passage shown under 
the jacket. The throttle sleeve, 3, regulates the air flow by 
controlling the exhaust; 6 is a bumper washer, fixed by the 



PNEUMATIC TOOLS. 



527 








; 



i if mm t 




528 



COMPRESSED AIR AND ITS APPLICATIONS. 



shoulders of the cylinder and nose-piece. The tool-holder is 
held back against the washer by a helical spring, 15; 1 1 is a 
U-shaped wire to keep the throttle nut 2 from turning; 12 is a 
helical spring to keep the throttle sleeve to its conical bearing ; 
14 is a spline shown at the top of the piston and fixed in the cyl- 
inder to keep the piston from revolving and displacing the air 
ports. This company also makes a valveless stone hammer 
equal to all the requirements of light stone-cutting and letter- 
ing, and containing but few working parts in its construc- 
tion. 

The pneumatic stone-dressing machine (Fig. 358) is one of 
the most convenient and best labor-saving appliances used in a 
stone-cutting establishment. A hammer of the larger dimen- 
sion, mounted on the end of a traveller running freely between 
rollers, suspended and balanced on a post resting on a truck, is 
a rig that gives complete control of the motion of the tool over 
the face of a block of stone. The hand easily guides the tool 




PIG. 359— LITTLE GIANT AIR DRILL. 



for evening the surface and for hammer dressing, a most tedi- 
ous operation when done by hand. The exhaust is at the 
top of the tool cylinder and is directed toward the cutter by 



PNEUMATIC TOOLS. 529 

a hose, thereby keeping the face of the stone clear of chips and 
dust for the inspection of the workman. 



AIR TOOLS OF THE STANDARD PNEUMATIC TOOL COMPANY, 
CHICAGO, ILL. 

We illustrate in figs. 359 and 360 the " Little Giant " revers- 
ible piston type air motors, used for all kinds of portable drill- 
ing, reaming, and tapping in the machine shop and in outdoor 




Fig. 360.— small two-piston motor drill. 

practice. The motor consists of four single-acting cylinders, in 
pairs, connected to opposite ends of a double crank shaft, so that 
the shaft receives four impulses at each revolution, and develops 
from i-§- to 3^- horse power, in the various sizes, at 80 pounds air 
pressure. 

This company also makes the " Little Giant " pneumatic 
hammers, air hoists, motor chain hoists, air car-jacks, stay-bolt 
nippers, and yoke riveters. 

COMPRESSED-AIR RIVETERS. 

Direct-pressure riveters are used as stationary machines for 
riveting boiler and tank shells. Their large pistons act directly 
upon the rivet, and they are quick-moving powers for this work. 
The toggle-joint movement with small piston and cylinder 
mounted on a portable frame has become the general type for 
structural work. The Allen yoke riveter is one of the types in 
which the toggle joint is pivoted to a cam bar and also within 
34 



53Q 



COMPRESSED AIR AND ITS APPLICATIONS. 



the trunk piston. By the differential or trunk form of piston 
the return stroke economizes the compressed air, while the 
large piston area gives great power to the riveting stroke. 

A double-lever riveter is sketched in Fig. 362, in which the 
air piston acts directly upon the toggle joint by drawing it to- 
ward the cylinder. It is balanced on a yoke. 

These sketches are from the early models of the Allen pat- 
ents. These riveters have been in practical operation for many 
years as standard pneumatic tools. They have been remodeled 





FIG. 361.— ALLEN MODEL. 



Fig. 362.— double lever riveter. 



and improved to meet the requirements of all kinds of struc- 
tural work, until there seems to be no place that a pneumatic 
riveter cannot reach, as shown by accompanying illustrations. 



PNEUMATIC RIVETERS OF THE CHESTER B. ALBREE 
IRON WORKS, ALLEGHENY, PA. 

■ The riveters of this company are of the toggle-joint type, 
giving the theoretically correct pressure due to the increasing 
resistance of the rivet during the driving stroke. A connecting 
bar holds the thrust member of the rolling toggle to prevent 
binding of the rivet piston, which is drawn back by a helical 
spring. A screw on the riveting die serves for adjustment of 
throw. A special design is shown in Fig. 363 for riveting col- 
umns, as the horn can be inserted between the channels and 
braces. Fig. 365 shows how easily the riveter may be inverted 
with the aid of the universal bail. 



PNEUMATIC RIVETERS. 



531 




t 




j^y 






532 



COMPRESSED AIR AND ITS APPLICATIONS. 



AIR HOISTS. 



The application of air hoists to cranes, over-lathes, planers, 
drilling machines, and, in fact, to all conditions in which a hoist 
may be useful, is now made in an almost endless variety of 
ways to meet the requirements of machine shop and foundry 




Fig. 365.— inverted on universal bail. 



practice. The most common type is the simple cylinder hoist, 
either vertical or horizontal, or in combination with an inter- 
mediate inelastic fluid, water or oil. 

In many instances direct-acting hoists may be readily ap- 
plied to hand-power cranes already in use, in which the hoist 
may be hooked to the gear tackle for adjusting the height, when 
the air hoist may be used for quick work. 



PNEUMATIC HOISTS. 



533 




Fig. 366.— safety 
stop air hoist. 



In Fig. 366 is shown the safety stop applied to the direct 
hoist for arresting the lift automatically at any desired point by 
closing the air valve, the lift being otherwise 
controlled by the three-way cock and double 
lanyard. 

THE OIL-GOVERNED PNEUMATIC HOIST OF 

THE CRAIG RIDGWAY & SON COMPANY, 

COATESVILLE, PA. 

The top head is enlarged to form a reservoir. 
To this head is secured a bar which has a pas- 
sageway through it connecting 
with the reservoir. This fixed 
bar passes through the piston 
and enters the hollow piston 
rod. A leather cup supplemented by any 
ordinary packing-box makes a tight working- 
joint at the piston with the fixed bar. In the 
reservoir are two valves, one a swing check 
valve and the other a simple regulating valve 
with a screw stem. The stem extends out- 
side the reservoir and is provided with a 
sprocket wheel for regulation. 

The action of the governing device is as 
follows: The piston is pulled down to the end 
of its stroke and ordinary machine oil is poured 
into the reservoir. It passes the valves and 
fills the hollow piston rod. If now full press- 
ure of air be under the piston and the valves 
be closed, the hoist cannot move, its move- 
ment being resisted by the fixed bar and the 
oil in the hollow rod. If now the regulating 
valve be opened, the oil will escape into the reservoir, and the 
hoist will rise just as fast as the oil can pass this valve, and no 
faster. It makes no difference how the air is admitted to the 



Fig. 367. — oil-gov 
erned hoist. 



534 



COMPRESSED AIR AND ITS APPLICATIONS. 



hoist, or whether the hoist is loaded or empty, its motion is 
controlled entirely by the oil. When the piston lowers, the oil 
passes back into the rod by the check valve. 

An air inlet valve is also connected with the upper and the 
under side of the piston. The under side of the piston is always 
connected to the compressor and always under pressure; the 
oil pan is also always under pressure. The valve admits air to 
and exhausts from the upper side of the piston. No air is con- 
sumed in lifting the load, the air being used to press the piston 
down the cylinder. The air being admitted above the piston, 




Fig. 368.— travelling crane and air hoist. 

pressure is equalized on both sides and the piston is forced 
down the cylinder with a force equal to the diameter of the pis- 
ton rod. The oil is forced into the rod by pressure. Gravity 
is not depended upon to lower the piston, and packings can be 
made and kept tight. No air from the shop ever enters the 
cylinder to carry in dirt and dust. All motions being under 
perfect control, and all done by pressure, jerkiness and danger 
are entirely overcome. The air pressure, being always under 
the piston, is like a big perfect spring; and with the oil to reg- 
ulate its upward motion, the Ridgway hoist reaches a high point 
of perfection. 



PNEUMATIC HOISTS. 



535 



TRAVELLING CRANE WITH AIR HOIST. 




The Ridgway air hoists are mounted in many ways to suit 
the wants of foundries and machine shops. The most common 
plan is to carry them upon travelling bridges, swing cranes, or 
runways. The cut shows a ten-ton hoist upon 
a traveller. The cylinder is hung in a gimbal 
truck, and is moved back and forth on the 
bridge by a pendant hand chain. The bridge 
is travelled by an air engine, operated by cords 
from the floor, or it may be arranged to move 
by hand. The crane is connected to the air 
supply at end of the runway by a hose. The 
hose is carried in sections by small trucks trav- 
elling upon one of the tracks of the runway. 
A better plan is to carry the hose by trucks or 
slides upon a special track over the centre of 
the span. Slides are preferred by some to 
trucks, in that they never get out of order or 
need attention. As the crane travels in one 
direction the hose stretches out one loop after, 
another. As it moves in the opposite direction 
the trucks or slides are pushed ahead and 
gather up the hose. 

In the smaller travelling crane of two-ton 
capacity, the hoist is carried b)^ a trolley run- 
ning upon the lower flange of a single I beam. 
In this case the hose is wrapped upon a reel, 
the air being taken in through the hollow axis 
of the reel. The reel is placed so the cylinder 
can move past it and cover the full span of the bridge. The 
hose is attached to the air supply at one end of the runway. A 
cord is run from the reel to the opposite end of the runway. 
The pull of the hose unwinds it from the reel as the crane 




Fig. 369. -air hoist. 




536 COMPRESSED AIR AND ITS APPLICATIONS. 

moves in one direction, while the pull of the cord winds up the 
hose as the crane moves in the opposite direction. 

The festoon and the reel plan are the two most approved 
ways of taking care of the hose. When it can be used the fes- 
toon plan will be found, 
on the whole, the cheap- 
est and best of the two. 

AIR HOISTS OF THE CUR- 
TIS MANUFACTURING 
COMPANY. 

The air hoists of this 

company are made in 

eleven sizes, from 3 to 

16 inches in diameter; 

and with standard lifts 

of 4 feet, or of special 

lengths when desired. 

These hoists have a 

rff ; ,'| ,,'. special self-closing valve 

ilpiL 2S' device, shown in the en- 

elll 1 -' larged view (Fig. 370) , by 

which a helical spring, 

\ H ^J attached by suspender 

r/\ ■ chains to each arm of the 

.; valve, brings the valve 

I joBjiiisJ i to its closure independ- 

' -**cLk ! fl ently of the operating of 

h the hand chains. 




_t j0 mm I y An adjustable stop 

} J operated by a set collar 

\ 1 on the piston rod stops 

h the load at any set point, 

by moving a rack and 

Fig. 370.— self-closing valve. pinion. 



PNEUMATIC HOISTS. 



537 




538 



COMPRESSED AIR AND ITS APPLICATIONS. 



It has also an adjustment for regulating the speed of the 
hoist independently of the valve movement. 




Fig. 372.— loading. 



THE AIR-HOIST TRAVELLER FOR STORES AND WAREHOUSES. 

For transferring goods in a ware- 
||^^|f^l|, house or factory, or for loading and 

unloading goods from trucks, nothing 
else has been devised that is so con- 
venient and cheap as the air hoist. 
The same power that operates the ele- 
vators will compress sufficient air for 
the operation of these handy devices. 
The overhead trolley rail is readily in- 
stalled and can be extended across the 
street or across alleyways between fac- 
tories, to facilitate the dropping or 
picking up of merchandise or machin- 
ery directly to or from the trucks. A 
boy, with this aid, can lift and convey loads that would otherwise 
require a gang of men. In Fig. 373 is shown a horizontal air 
lift installed on an overhead 
trolley rail, for shops or stores 
where the ceiling is too low 
to accommodate a vertical 
lift. With long trolley rails 
winding among the machin- 
ery of a factory, the air pipes may be laid 
around the works with outlets and hose at con- 
venient places, which may be uncoupled when 
the load is lifted for long-distance runs. 

In Fig. 374 is shown the arrangement of 
the overhead trolley track, trolley, and sheaves 
for holding the hose as it is run out from the 
reel or hose drum. An arm on the trolley truck FlG 373 ._hoisting. 




PNEUMATIC HOISTS. 



539 



allows the hose to pass over the sheaves and be drawn forward, 
or to be pulled back by the hose drum, which has sufficient 
tension to keep the hose from dropping into inconvenient loops. 




Fig. 374.— the overhead trolley and host, sheaves. 

The drum reel (Fig. 375) is counterbalanced by a weight 
and rope wound upon a smaller drum on the same shaft. A 
sprocket and chain drives a guide screw carrying a nut, frame, 
and sheaves to guide the winding of the hose in its proper place 




-the hose drum and guide screw. 



54Q 



COMPRESSED AIR AND ITS APPLICATIONS. 



on the reel. The end of the hose is connected with the hollow 
shaft, from the end of which a stuffing-box allows the hollow 
shaft to turn freely in a fitting connected to the air-pipe line 
from the air-compressor receiver. 

The above illustrated goods hoist and conveyor is in opera- 
tion at the Nason Manufacturing Company, New York City. 
Patent of Carleton W. Nason. 

THE PNEUMATIC HOIST IN THE FOUNDRY. — AIR HOIST OF THE 
CHICAGO PNEUMATIC TOOL COMPANY. 



In no other operation in the foundry, save the air blast, is 
air used to such advantage as in air hoists and cranes ; and not 

least in the sand rammer. By 
using direct-acting air hoists 
suspended from trolley tracks, 
swinging, and travelling 
cranes, a vast amount of heavy 
labor is saved. Saving is the 
measure of our living in these 
competitive times. 

With overhead trolley rails 
and air hoists with detachable 
hose couplings, castings can be 
readily conveyed to any part of 
the foundry, or outside of the 
building to the machine shop. 
Few realize how cheap an 
air hoist is to operate, apart 
from its convenience and speed in handling loads. It has been 
estimated that compressed air at 90 pounds pressure costs about. 
5 cents per 1,000 cubic feet of free air, or 143 cubic feet of 
capacity in the air lift. 




-PILING AND STORING CAST-IRON 
COLUMNS. 



PNEUMATIC HOISTS. 



541 



Fig. 377.— air lift, style 3. 
With releasing' valve. 



Fig. 378.— air lift, style 6. 
Diameter, 3 to 6 inches. 



542 



COMPRESSED AIR AND ITS APPLICATIONS. 



COMPRESSED-AIR APPLIANCES OF THE PEDRICK & AVER 
COMPANY, PHILADELPHIA, PA. 

The pneumatic lifts of this company are made with seamless 
hard brass tubing, with heads bolted through, and in three 
styles, viz. : 

No. i style has only one valve for admitting and releasing 
air. With this valve, the instant the hand releases the operat- 




. 



FIG. 379.— NO. 4. STYLE ON TRAVELLING CRANE. 

3 to 16 inch cylinders, with any desired valve and controlling appliance. 

ing chain (either when raising or lowering the load) the valve 
is automatically closed by the air pressure, thus shutting off the 
admission or discharge of the air and stopping the load at that 
point. 

No. 2 style is fitted with two valves. One valve is for ad- 
mitting and releasing the air in the cylinder and is left open to 
the supply when lifting the load. The second valve is con- 




FlG. 380.— THE HORIZONTAL HOIST. 

With sheaves for draw hoist, 2 to 1, for travelling cranes and boom hoists. 



PNEUMATIC HOISTS. 



543 



trolled by a loose collar with a set screw, on the piston rod, 
which is adjusted for the height of the lift desired. When the 
load is lifted to this height this second valve automatically 
closes, cutting off the supply of air; then, in case of leakage 
from any cause, it automatically admits just enough air to keep 
up the supply and retain the position of the load. 

No. 3 style has three valves, the first two valves being 
identical with those of the No. 2 style, and with all their ad- 
vantages, while the third valve is called a releasing valve and 




Fig. 381.— Horizontal multiple hoist 
On a free running trolley for cranes and booms. 

sustains the load perfectly stationary when it varies in weight 
while suspended, as pouring out molten metal, etc. This is 
obtained by the automatic action of these valves releasing or 
admitting air into the hoist cylinder as is necessary to keep the 
load in the same position. 

Air-Lift Work. 

















Amount 








of free air 








of free air 


Diam- 
eter. 


Capacity. 


Lift. 


consumed per 

4 foot lift 

at 80 pounds 

pressure. 


Diam- 
eter. 


Capacity. 


Lift. 


consumed per 

4 foot lift 

at 80 pounds 

pressure. 


Inches. 


Pounds. 


Feet. 


Cubic feet. 


Inches. 


Pounds. 


Feet. 


Cubic feet. 


3 


470 


4 


I.I7 


9 


4.440 


4 


IO.88 


4 


930 


4 


2.13 


10 


5,630 


■ 4 


I3-50 


5 


1,400 


4 


3-31 


12 


8,015 


4 


19.58 


6 


1.925 


4 


4-83 


14 


10,803 


4 


26.51 


7 


2.660 


4 


6.63 


16 


14,123 


4 


34-49 


8 


3,660 


4 


8.67 











544 



COMPRESSED AIR AND ITS APPLICATIONS. 



The style shown in Fig. 379 is for use in foundries or in 
connection with sheave attachments, where the slightest move- 
ment of the hoist while suspending the load is undesirable. 
This is prevented by a specially arranged valve by which air is 
constantly on both sides of the piston, preventing jumping of 
the piston and giving a slow, steady movement in lowering or 
raising, and yet admitting of a quick movement when necessary. 



THE DIRECT-ACTING PNEU- 
MATIC-CHAIN JIB CRANE. 

Admitting compressed 
air on the top of the piston 
by a valve on the back of 
the mast, it is forced down- 
ward and pulls with it the 
piston rod to which is at- 
tached a chain running over 
a sheave under the top pin- 
tle and out to the end of 
the jib which lifts the load. 
By releasing the air on top 
of the piston the counter- 
balance on end of chain 
falls, lifting piston into po- 
sition ready to lift next load. 
Sheave wheels and top pin- 
tle of mast are furnished 
with roller bearings, bottom 
pintle of mast having ball- 
and-socket bearing. The 
height of lift is limited only 
by the head room ; and 
where conditions are such 
that the load does not have 




DIRECT-ACTING PNEUMATIC CRANE. 



PNEUMATIC PUNCH. 



545 



to be moved along the jib, this style of crane is particularly 
desirable on account of its simplicity. 

In Fig. 383 is shown a section of the Pedrick & Ayer oil- 




pneumatic riveter, in which by the use of differential pistons the 
elastic compression of air at moderate pressure controls a small 
piston acting upon an inelastic fluid (oil) for generating a high 
pressure upon the dolly-bar or riveting piston. Referring to 



15 



546 



COMPRESSED AIR AND ITS APPLICATIONS. 



the sectional cut, the movement of the lever 15 operates the 
cylindrical three-way valve 12, for driving the piston of the air 
cylinder and its plunger 18, which passes through a stuffing 
box 44 into the oil chamber, producing a pressure equal to the 
differential areas of the air piston 39, plunger 18, and the dolly- 
bar piston 13. In this way a comparatively small air cylinder 
at 80 pounds air pressure may be made to exert a pressure of 



^ 




Fig. 384.— the lattice or column riveter. 

from 10 to 15 tons on a rivet head. A free floating piston, 23, 
in a small separate cylinder, is made by air pressure to follow 
up the oil charge in the oil chamber as the dolly moves down 
to the rivet, and allows the oil to be drawn back by the return 
of the oil plunger and through the air pressure on the push- 
back piston on the dolly -bar 28. A rear-end view is also shown 
at the left, indicating the position of the oil cylinder with its 



PNEUMATIC PUNCH. 547 

the riveter with oil, the floating 



floating piston. In chargin 

piston is drawn to the back end of the cylinder by removing 

the plug 35 and inserting the pull rod 48. 




COMPRESSED-AIR PUNCH. 

In Fig. 385 is illustrated a simple and compact air punch; 
a most convenient and easily handled punch for sheet and plate 
work. It is made by the F. F. Slocomb Company, Wilming- 
ton, Del., and consists of 
a hollow piston adapted 
to contain oil and fitted 
with a prolongation or 
tail rod, within which 
tail rod a stationary tube 
seated in the hook is 
adapted to telescope ; the 
oil being thereby forced 
into and through the 
stationary tube and 
thence upon the plunger 
into the vertical cham- 
ber of the hook, where 
it exerts accumulated 

pressure. The air that FIG - sss-casey pneumatic punch. 

drives the piston during the stroke is utilized to drive it back 
for another, being finally expelled through the exhaust during 
the next succeeding stroke. This effects an important saving 
in the quantity of air used. 

The cylinder, cap, and hollow piston are made of aluminum 
in order to make the machine as light as possible. It is a great 
saver in time and help in sheet metal, plate, and light struc- 
tural work. 

The smallest size, No. o, punches y^-inch metal and under, 
and weighs but 28 pounds, using -^ cubic foot free air per stroke. 



548 COMPRESSED AIR AND ITS APPLICATIONS. 

No. i punches up to f-inch metal, weighs 143 pounds, and uses 
1 cubic foot free air per stroke. No. 2 punches f-inch metal, 
weighs 775 pounds, and uses 3 cubic feet free air per stroke. 
No. 3 is a still larger machine adapted for heavy punching, 
using 5 cubic feet free air per stroke. 



COMPRESSED AIR IN RAILROAD SHOPS. 

There seems to be no end to the use of compressed air 
in railroad-car construction and repair shops. Besides driv- 
ing motors for drilling, reaming, and wood-boring; hammers 
for chipping, riveting; motors for running special machines; 
lifts, jacks, and many other devices described in this work, we 
may add a pneumatic press for bending eye-bolts, brake-hanger 
hooks, bar-straps for braces, and truck-frame construction. 
The horizontal pneumatic press, called the bulldozer, mounted 
on a strong frame with abutting anvils, with the frame on wheels 
for portability, is a handy helper for the power to easily ac- 
complish a great variety of work in the car shop. It is a won- 
derful blacksmith helper in bending, upsetting, and riveting on 
the parts of locomotive and car work, upon which a large num- 
ber of processes are necessarily duplicated. The stationary 
pneumatic hammer in the blacksmith shop is a most useful ap- 
pliance, and does away with the discomforts of the steam ham- 
mer by giving fresh, cool air to the workers. Pneumatic 
punches and shears are among the useful tools not here illus- 
trated. The portable sand-papering disc and the emery wheel 
are now driven by a rotary air motor. 

The stay-bolt cutter operated by the direct pressure of air is 
one of the handy tools in the boiler shop. The shearing off of 
stay bolts is tedious work when done by hand. A balanced 
stay-bolt cutter or shears operated by direct-air pressure and 
the double toggle joint and lever, as shown in Fig. 386, has an 
immense power for cutting and shearing. Thus a cylinder only 
10 inches in diameter at 60 pounds air pressure gives a gross 



PNEUMATIC TOOLS. 



549 



pressure to the toggle and levers of 4, 700 pounds ; which mul- 
tiplied by a leverage of 3 is equal to 7 tons ; which again in- 
creased by the size of the angle of the toggles may be made 
to apply a pressure of 40 or more tons 
to the biting jaws, accomplishing work 
in a few seconds that would otherwise 
require several minutes. This gain 
counts in the day's or week's work, and 
soon pays in every department for a 
complete equipment in compressed-air 
appliances. 

One of the many useful tools oper- 
ated by compressed air in the locomo- 
tive-boiler shop is the bolt-nipper, of 
which one type of air-operated nippers 
has cut off in one case all the stays in the firebox of a Brooks 
"ten-wheeler" in three hours, and was handled by two boys, a 
job which formerly occupied a boilermaker and helper nearly 
two days. This is a saving in cost of about 90 per cent, and 
the same work with this tool in another erecting shop resulted 
in a saving of 86 per cent. The nippers cutting off from both 
sides at once, do not injure the sheet or loosen the thread, as 
may be done by chipping the stays off. . ... 




Fig. 386.— stay-bolt cutters. 







FIG. 3S7.-THE PNEUMATIC STAY-BOLT bitek. 



Two strong pivoted levers operated by an air piston. No. i will cut stay- 
bolts up to 1 inch diameter, and No. 2, up to i^ inch diameter. 



55o 



COMPRESSED AIR AND ITS APPLICATIONS. 



Figs. 388 and 389 are a front view and side section of a car- 
wheel jack, used for loading fitted-up car-wheels upon platform 
cars for transportation. Fitted to the head of the pneumatic 
piston is an arm with bearings which engage the axles and lift 
them to the level of the platform car upon which they are to be 




Fig. 388.— pneumatic car-wheel jack. 



FIG. 389.— SECTION OF CAR-WHEEL 
JACK. 



loaded. By this device the many accidents to laborers loading 
in the old way by skids are entirely eliminated. 

The jack is usually a cast-iron cylinder sunk in a pit be- 
tween the rails of the track on which the wheels are to be 
loaded. 

Apart from the many pneumatic tools used in railroad 
shops described and illustrated in other parts of this book, we 
may mention the pneumo-hydraulic rail-bender and straight- 
ener, the pneumatic machine for putting on air-brake hose, a 
troublesome job to do by hand, and the pneumatic car-lifting 



PNEUMATIC TOOLS. 



551 




^> 



Fig. 390 —pull-down jack. 




Fig. 391.— section, pull-down jack 




Fig. 392.— section, pneumatic motor s\w. 



552 COMPRESSED AIR AND ITS APPLICATIONS. 

jacks and presses for putting car-wheels on their axles, and for 
removing them. 

The pull-down jack is similar to the lifting jack, only that 
it has a double-acting piston, and its special use is in repairing 
cars, for removing draft timbers and sills. It is illustrated in side 
view and section in Figs. 390 and 391. It is moved on truck 
wheels by a thill handle, and can be used also as a lift. 

Fig. 392 shows a small, direct-connected motor saw, operated 
in the hands of workmen. It is used much about the body work 
on cars, and for cutting off the ends of car roofs. 



Chapter XXV. 



AIR AS APPLIED TO 
PYROMETRY 



AIR AS APPLIED TO PYROMETRY. 

Air, unlike metals, is a perfect thermometric or pyrometric 
substance. The action of the air pyrometer is based on a prin- 
ciple which involves the law of the flow of air through small 
apertures. The development of the instruments has extended 
over a considerable period of time, and the air pyrometer has 
been on the market in its present form during the past five years, 
being now recognized as an absolute standard in the determina- 
tion of high temperatures. 

Its application covers a wide field, comprising principally 
the measurement and autographic recording of the temperature 
of the hot blast, the escaping gas of a blast furnace, and the 
determination of the heat of annealing and tempering furnaces; 
by a knowledge and record of which steel can be treated accu- 
rately and with consistent results. It is essentially a device 
adapted to practical working conditions, cannot be injured ex- 
cept through mechanical abuse, and will give the same relative 
readings month after month irrespective of whether it is used 
constantly or intermittently. This last, together with the fact 
that it is a recording pyrometer, establishes its chief value 
in industrial operations, for if the calibration of a pyrometer 
changes with time, and the readings are relied upon to regulate 
the temperature, even worse results will be obtained than where 
no determinations are made. The record renders it possible 
for the one in charge to know definitely whether or not his in- 
structions are being followed, and furnishes a guide for future 
operations. 

The complete apparatus consists of three parts : the regula- 
tor, or main portion of the instrument; the fire tube, or part 
applied to the heat which is connected with the regulator at 



556 



COMPRESSED AIR AND ITS APPLICATIONS. 



any distance from 10 to 300 feet; and the recording gauge, 
which is also connected to the regulator, and by means of which 

a record of the tem- 
perature is printed on 
a strip of paper. 

The regulators are 
made in two forms, 
known as single and 
double. The first 
permits of the attach- 
ment of one fire tube 
and one recording 
gauge,. and the second 
of two fire tubes and 
two recording gauges, 
so that in the latter 
case the heat may be 
measured in two 
places at the same 
time. 

The fire tubes are 
made in two forms, 
blast furnace and port- 
able ; the former 
being used exclusively 
at blast furnaces, 
while the latter, asim- 
k plied by its name, is at- 
tached to the regulator 
by a flexible connec- 
tion which permits of 
its use at any point 
within a radius equal 
to the length of this connection. This form of fire tube is 
used on annealing and tempering furnaces and for similar pur- 




[R PYROMETER. 



AIR AS APPLIED TO PYROMETRY. 557 

poses, the regulator and recording gauge being located cen- 
trally so that the fire tube can be inserted successively in any 
one of a number of furnaces or allowed to remain for a greater 
or less time in any one furnace as desired. The blast-furnace 
fire tubes can be used with either the single or double regulator, 
as can also the portable fire tubes. 

The recording gauges vary only in their calibration, this 
being governed by requirements. They can be so adjusted 
that the limiting lines of the record shall be 200 and 3,000° 
F., or any intermediate points may be chosen, such as 500° 
and 1,500°, 1,000°, and 3,000°. Either the Fahrenheit or Cent- 
igrade scale is obtainable. 

Fig. 393 shows a single pyrometer. On the left is the regu- 
lator, and connected to it on the right is the recording gauge ; 
a portable fire tube rests against the recording gauge. On the 
front of the regulator is a scale graduated from 100° to 1,400° 
C, or from 200° to 3,000° F. When the instrument is in oper- 
ation the temperature to which the fire tube is subjected is 
shown at all times by the water column on front of scale. 

Fig. 394 shows the recording gauge. The record is on a 
continuous strip of paper, and the scale is very open. The rec- 
ords can be removed ever}' day, once a week, or once a month 
as desired, the back record being always accessible if the charts 
are detached at long intervals. 

As previously stated, the pyrometer is based on the law gov- 
erning the flow of air through small apertures. Referring to 
Fig. 395, if two such apertures, A and B respectively, form the 
inlet and outlet openings of a chamber, C, and a uniform suc- 
tion is created in the chamber C by the aspirator D, the action 
will be as follows : 

Air will be drawn through the aperture B into the chamber 
C ', creating suction in chamber C, which in turn causes air from 
the atmosphere to flow in through aperture A. The velocity 
with which the air enters through A depends on the suction in 
the chamber C, and the velocity at which it flows out through 



558 



COMPRESSED AIR AND ITS APPLICATIONS. 



B depends upon the excess of suction in C over that existing 
in the chamber C, that is, the effective suction in C. As the 
suction in C increases, the effective suction must decrease, and 
hence the velocity at which air flows in through the aperture 




Pig. 394.— the recorder. 

A increases, and the velocity at which air flows out through the 
aperture B decreases, until the same quantity of air enters at 
A as passes out at B. As soon as this occurs no further change 
of suction can take place in the chamber C. 

Air is very materially expanded by heat. Therefore the 
higher the temperature of the air the greater the volume, and 



AIR AS APPLIED TO PYROMETRY. 



559 



the smaller will be the quantity of air drawn through a given 
aperture by the same suction. Now if the air, as it passes 
through the aperture A, is heated, but again cooled to a lower 
fixed temperature before it passes through the aperture B, less 
air will enter through the aperture^ than is drawn out through 
the aperture B. Hence the suction in C must increase and the 
effective suction in C must decrease, and in consequence the 
velocity of the air through A will increase, and the velocity of 
the air through B will decrease, until the same quantity of air 
again flows through both apertures. Thus every change of 
temperature in the air entering through the aperture A will 




Fig. 395.— the principle. 

cause a corresponding change of suction in the chamber C. If 
two manometer tubes, p and q (Fig. 395), communicate respec- 
tively with the chambers C and C, the column in tube q will 
indicate the constant suction in C, and the column in tube/ 
will indicate the suction in the chamber C, which suction is a 
true measure of the temperature of the air entering through 
the aperture A. 

In its practical application the aperture A (Fig. 395) must 
be so located that the air before passing through it shall acquire 
the temperature which is to be be measured, and this is accom- 
plished by placing it at the end of a small platinum tube e (Fig. 
396), this being enclosed within a larger tube d of the same 
material, so that the aperture A comes within a short distance 



560 



COMPRESSED AIR AND ITS APPLICATIONS. 



of the closed end of the tube d which protects it. Both tubes, 
d and e, are brazed into drawn copper tubes, c and /, the length 

of which depends on the length 
of the water-cooled jacket F. 
The tube c is soldered into the 
coupling piece c . The tube / 
terminates in a flanged head/', 
and is secured to the coupling 
piece c' by the follower g' and 
nut c" . This combination is 
called the "fire tube." 

The fire tube is placed within 
a water-cooled jacket F, which is 
fed by water entering at y and 
escaping at z. This jacket pro- 
tects those parts of the fire tube 
that are susceptible to injury 
by heat. The aperture A, being 
thus disposed, can be readily lo- 
cated so that the air must have 
' attained the temperature of the 
furnace before passing through. 

As shown above, the air passes 
in at b and thence between tubes 
d and e through aperture A and 

FIG. 396.-PYROMETER TUBE AND PLUG. into tube ^ being drawn frQm 

here to the regulator through an air-tight connection. In order 
that this air shall be perfectly clean and thus avoid clogging 
the small aperture A, it passes through a cotton filter before 
going in at b. This cleans it thoroughly. 

It is also necessary to so locate aperture B (Fig. 395) that 
before passing through it the air shall acquire a fixed tempera- 
ture, and to provide for this it is placed within a coil and the 
coil surrounded by steam at atmospheric pressure. This se- 
cures a uniform temperature of 212 F., and the method of 




AIR AS APPLIED TO PYROMETRY. 



5 6l 



arrangement can be seen in Fig. 397, where B is the aperture, 
G a pot into which exhaust steam from the aspirator is led, and 
t' the large-volume drain pipe carrying off the steam and con- 
densed water. 

The operation of the instrument will be understood by re- 
ferring to Fig. 398, which is a diagrammatic disposition of the 
parts. The interior of the pipe, e, /, g, k, i, from aperture to 
aperture, together with the branches q and s, constitute the 
chamber C of Fig. 395. Its inlet from the atmosphere is 
through the opening a at the bottom of the filter /, and its 
connection with chamber C is 
through the pipe i. 

The aspirator D exhausts into 
the chamber G, keeping it at a 
constant temperature of 212 . 
The steam and condensed water 
escape through the pipe / at 
atmospheric pressure. Opening 
the valve 6 steam enters the as 
pirator D, and sucks the air 
through the tube m, out of the 
chamber C, and produces a suc- 
tion, which is kept constant by 
the regulator H as shown by the 
manometer p. With a constant 
suction in C and cocks 2 and 
4 open, air will enter at a, pass 
through the filter I, where it is 
purified, then through the con- 
nection b into the fire tube. It 
flows forward in the space between the two tubes c and /; as 
soon as it reaches the platinum tube d, which protrudes from 
the cooler, it becomes heated and enters through the aperture 
A into the chamber C, at the temperature surrounding the ex- 
posed end of the fire tube, which is the temperature to be 
36 




Fig. 397.— steam heater. 



562 



COMPRESSED AIR AND ITS APPLICATIONS. 







FiG 398.— DETAILS OF THE AIR PYROMETER. 

Uehling-Steinbart Company, Carlstadt, N. J. 



AIR AS APPLIED TO PYROMETRY. 563 

measured. After passing A, the air flows through the pipe e, 
f, g, h, into the coil i, where it assumes the temperature of 
212 , at which it passes through aperture B, thence by the con- 
nection /' into the chamber C , from which it is drawn by the 
aspirator D through ;//, and discharged with the exhaust steam 
and condensed water. 

The branch pipes s and q' connect respectively with the re- 
cording gauge L and the manometer q, which is placed in front 
of the temperature scale on the regulator. 

This detailed description of the working principle of the 
pyrometer may lead to the belief that it is complicated and not 
readily kept in order. Such is not the case, for it must be 
remembered that the only moving parts, aside from the record- 
ing device, are steam and air. Wear is thus eliminated, and 
the continuous use of the instruments under the most adverse 
conditions attests their practical merit. 

THE ELECTRIC CURRENT INDICATING METER. 

The principle on which the operation of these meters are 
based consists in causing the variations in the electric current 
to be measured to control the variation in pressure of a body of 
air in a closed vessel, this variation being in turn indicated by 
the rise and fall of a column of non-volatile liquid in a glass 
tube, back of which is secured the scale. 

In Fig. 399, assume that some source, say a small pump, is 
delivering air at a fairly constant pressure of about if pounds 
per square inch through the pipe A. This enters the chamber 
B and then flows through a series of porous diaphragms made 
of filter paper whose function is to serve as an air resistance, 
incidentally serviro; to remove any dust particles. The air 
then enters the passage D into which is drilled the opening E 
which is capped py the valve F. 

The valve cWsists simply of a small flat disc of non-oxidiza- 
ble metal F resting on a circular seat with escape ports G below 



564 COMPRESSED AIR AND ITS APPLICATIONS. 




Switch bo arcL ■ 



1-^ 





^ 


^ -N 


\ 




M 




M 


ik 




,L^| 






I 


i T ^ 





*-o 




Fig. 399.— column type, electric current indicating meter. 
Machado & Roller, New York City. 



AIR AS APPLIED TO PYROMETRY. 565 

it and a pin H resting on top. On the pin rests a spool J car- 
ried by one end of the lever /, on the other end of which is a 
counter-weight K, by means of which the effective weight on 
the pin H can be adjusted. 

The spool is wound with wire through which the current to 
be measured is passed, this being done via the two short thin 
copper ligaments L which support and form the pivots about 
which the lever can oscillate. 

A magnet M furnishes a field of force such that the reaction 
between it and the current pimels the spool down with a force 
increasing as the current increases. The valve i^is thus a vari- 
ably loaded safety-valve whose blowing-off point is constantly 
and proportionately varied by the current variation. The 
counter-weight K on the lever is so adjusted that when no cur- 
rent is passing through the spool the weight on the valve pin 
is such that the blowing-off pressure in D is sufficient to force 
the liquid in the closed chamber TV up through the glass tube 
O to a height R, which therefore is the zero of the scale. The 
pressure cannot go above this when no current is on, as any 
tendency to increase simply results in lifting the valve slightly 
higher, whereupon more air escapes and the pressure falls back ; 
nor can it go lower, for if there were this tendency the valve 
would partially close because of the spool weight, and the less 
rapid escape of air through it would cause the pressure to build 
up again because of the constant flow of air from the high- 
pressure supply at A through the air resistance C. 

Exactly the same thing holds good when the weight on the 
valve is that due to the non-counterbalanced portion of the 
spool weight plus the downward thrust caused by a given cur- 
rent through it. This gives what is practically a heavier loaded 
safety valve, so that the blowing-off pressure in N is higher, and 
this higher pressure of course forces the liquid up further in 
the glass tube, thus showing the presence of a current. The 
height to which the liquid rises is directly a measure of that 
current, because the extra downward thrust on the spool is, 



566 



COMPRESSED AIR AND ITS APPLICATIONS. 



from the magnetic field and spool design, proportionate to the 

current. 

The air resistance C not only prevents the action from being 

so sudden that the indications are not dead-beat, but in the case 

of a decrease in current strength allows the air in the closed 

chamber N to flow 
back promptly and so 
register the decrease. 
The glass tube being 
but 24 inches long, the 
pressure at A (equiva- 
lent to about a 49-inch 
column of the liquid) 
is always sufficiently in 
excess of that in the 
passage D and the 
chamber N to cause the 
changes to be promptly 
registered. 

From the foregoing 
it is seen that the zero 
adjustment is made by 
screwing in or out the 
counter-weight K, thus 
shifting all scale values 

FIG. 400. -ELECTRIC AIR COMPRESSOR. ^ equa] distance Up 

or down the tube. For actual calibration before shipment an 
iron screw 5 of heavy cross-section is provided, which, on being- 
brought closer to or further from the opposite leg of the mag- 
net, weakens or strengthens the field in which the active spool 
works by shunting a portion of the lines. 

It should also be noted that the only work that the varying 
current has to perform is to control the air pressure. 

To furnish the air required for the operation of the column 
type of instruments, this is one of two separate types of devices. 




AIR AS APPLIED TO PYROMETRY. 50/ 

The first is a simple, single-cylinder, single-acting air pump, 
mounted on a square iron box which serves as an air reservoir, 
and driven by a one-twentieth horse-power motor suspended 
underneath and connected to the pump by a belt. This type is 
of sufficient capacity to run fifty indicators or twelve recorders, 
the construction of the latter being such that they require 
nearly four times as much air as the former. 

The motor is furnished for either a 1 10 or a 220 volt circuit, 
and for either direct or alternating current, as may be desired. 

The second type is a water-operated compressor, which 
operates like an injector, the water carrying the air with it and 
compressing it to the desired point. These require about ten 
gallons of water per hour per instrument, with 3-foot head, 
and are built in sizes to suit the particular installation. 

THE COMPRESSED-AIR ELECTRIC RECORDING METER. 

This is the same in principle as the indicating type de- 
scribed on the preceding pages. Instead, however, of employ- 
ing a rising and falling liquid column in a glass tube to give 
visual indications of the current changes, the column is made of 
much larger diameter and carries a hollow float supporting a 
rod with a pen at the extremity thereof, which in turn traces a 
line on a sheet of paper carried before it by a clock movement. 

By making the column diameter of a proper size the pen 
friction becomes negligible compared to it, and the .pen can be 
made to carry a supply of ink sufficient for long records without 
having this varying weight destroy the accuracy of the indica- 
tions. 

The illustration (Fig. 401) gives a section of this recorder, 
similar parts being lettered the same as those in Fig. 399. It 
will be noted, as above stated, that the only additions comprise 
the float P, the rod Q, and the pen R, together with the drum 
S, which is rotated one inch an hour by internally placed clock- 
work, and to the surface of which is secured the record paper. 



568 



COMPRESSED AIR AND ITS APPLICATIONS. 




FIG. 401.- SECTION OF the volt and ampere recording and indicating meter. 



AIR AS APPLIED TO PYROMETRY. 569 

Particular attention is invited to the fact that, owing to the 
absolutely dead-beat indications which this class of apparatus 
gives, the meters never run over; i.e., any fluctuations shown 
by them are true fluctuations, and their values are not added to 
by the inertia of the moving parts. 

Another unique feature that these devices possess is this : 
By drilling an additional hole through the cap forming the top 
of the chamber in which the liquid is contained, and connecting 
this by a tube with a second closed vessel U, similar to N in 
Fig. 399, the liquid in the tube dipping into this vessel will rise 
and fall with the rise and fall of the pen, as the variation in the 
pressure of the air therein is the same as that in the recorder 
chamber. In this way it is possible to put the recorders them- 
selves in the superintendent's office or elsewhere so that they 
cannot be tampered with, and place the pilot indicator on the 
switchboard so that the attendant will have before him a con- 
stant indication of what the recorder is doing. 

The sole manufacturers of the pyrometric and pneumatic 
volt and ampere meters are the Uehling-Steinbart Company, of 
Carlstadt, N. J. 



Chapter XXVI. 



COMPRESSED AIR IN 
RAILWAY SERVICE 



COMPRESSED AIR IN RAILWAY SERVICE. 

It is now forty years since compressed air for street-railway 
propulsion was agitated and began to take on form in plans for 
putting this system into practical operation. Although high 
air pressures had then and previously been produced in an ex- 
perimental way, the high-storage pressures of the present time 
were then scarcely dreamed of for practical work. The air- 
propulsion schemes seem to have slumbered until Captain 
Beaumont started a compressed-air passenger car with rising 
storage pressures that finally reached 1,000 pounds, at which 
the conditions of receiver construction for storage seemed to 
have reached a limit. At this time (1876), Mekarski was advo- 
cating and putting into practice, in France, the system of re- 
heating by hot water and using the evaporated water at high 
temperatures with the air, and on this system mine-hauling 
locomotives were operated. The first air-motor car was run in 
Paris in 1876. This was soon followed by the building of com- 
pressed-air railways at Nantes, the suburban roads of Vincennes 
and Nogent near Paris. In 1890 the Berne, Switzerland, city 
and suburban railways were opened for operation. The storage 
pressure there used was 470 pounds, while the car-storage press- 
ure was limited to 440 pounds per square inch. An extended 
investigation of the operating expenses of this road was made 
at that time, and was found very favorable to the compressed-air 
system, being 17 cents per car mile. 

The conclusions derived from the investigation of the 
Mekarski system at Berne for urban and suburban tramway 
traffic consisted in the pleasing appearance of the motor cars, 
in the absolutely smooth and noiseless motion, and the total 



574 COMPRESSED AIR AND ITS APPLICATIONS. 

absence of smoke, steam, or heat; that it had fully vindicated 
this system as preferable to any other system of tramway trac- 
tion. At Marseilles, France, the compressed-air tramway stor- 
age pressure is 1,200 pounds per square inch. 

The reheaters of this system are illustrated in the chapter 
on reheating. The Hardie system was first on trial on the 
Second Avenue Railroad in 1879 ( Fi g- 4° 2 )- 

This system was started in Toledo, Ohio, and in Westfield, 




Mass., about 1892, but from some constructive difficulties was 
changed to electric propulsion. 

The Judson system was originally instituted in a revolving 
drum under the track, driven in sections by compressed-air 
motors with air compressed in a central station and distributed 
to the motors through an underground pipe system. This fail- 
ing in expectations, the Judson system was changed to direct 
motor traction with the air heated by a small furnace containing 
a coiled pipe near the motor, in which the air was reheated after 
passing the reducing pressure valve, thus giving the best effect 
of reheating in the economy of air power. 

This system finally gave way to the Hardie improvements 
on the Mekarski system, and is now in use in Chicago, 111., 



COMPRESSED AIR IN RAILWAY SERVICE. 



575 




i s 




Fig. 404.— the judson system in Chicago, ill. motor passenger car and trailer. 



5/6 



COMPRESSED AIR AND ITS APPLICATIONS. 



with passenger motor cars, with or without trailers to suit the 
necessity for traffic accommodation. 

In Fig. 406 are represented some details of these motor cars, 
in which the piston in the cylinder H is connected by rod with 
a rock shaft for transferring the line of force to the outside of 




MS 



pi 



3 2 2 

p OR 



' ^ s ^ 

o -d £ o 



O .S -r 



3 0) 
P. ft. 



the wheels through the connecting rod P pivoted to the parallel- 
rod connection to the fore and aft wheel cranks. L is the brake 
cylinder, and F one of the high-pressure bottles. M M are 
columns in which are placed the controlling gear with their 
handles at N. 



COMPRESSED AIR IN RAILWAY SERVICE. 



577 




A 



t=*fc: 



In Fig. 407 is illustrated a section 
of the Hardie motor car of the type 
used on 125th Street, New York City, 
showing the location of the high- 
pressure air tanks B, C, D, E, F, and 
the reheating tank A ; the reducing 
valve at G and the motor cylinder at 




Fig. 407.— section, hardie motor car. 

H. The air passes from the high- 
pressure tanks to the reducer, then to 
the reheater, discharging beneath the 
water and taking on its temperature, 




I'HE AIR-PRESSURE CARD. 



and is saturated with vapor at a press- 
ure of 150 pounds; then to the con- 
trolling valve and expanded in the cyl- 
inders to near the atmospheric pressure under normal condi- 
tions of running. In Fig. 408 is an indicator card from 
37 



578 



COMPRESSED AIR AND ITS APPLICATIONS. 




I i 

O <a 

s IS 



COMPRESSED AIR IN RAILWAY SERVICE. 579 

these motors showing a mean pressure of about 40 pounds 
at i cut-off. 

In Fig. 409 are detailed a plan and elevation of a Hardie 
motor car, the various parts of which may be measured by the 
figured scale of the elevation, and in Fig. 405 an outside view 
of the same style of car now running on the 28th and 29th 
Streets line of the Metropolitan Railway Company, New York 
City. Similar cars are running on the street railway system at 
Rome, N. Y. 

The motor cars of the Compressed Air Company, New 
York City, are similar, in size and appearance, to standard elec- 
tric or cable cars, and can be operated at any desired speed. 
The type of car now in operation weighs about 22,000 pounds. 
All its machinery and storage apparatus are placed below the 
body proper. The motor and storage are supported and carried 
on independent frames and springs which relieve the axle of 
all pounding and hammering on the track. 

The engines of these cars have two cylinders, 7-inch diame- 
ter, 14-inch stroke, with driving-wheels of 16-inch diameter. 
They are equipped with air brakes operated by the same air 
that runs the motors. The operating levers are placed on the 
platforms, are simple in form, and of such design that no con- 
fusion can arise in the manipulations of the operator. 

The storage apparatus consists of sixteen air reservoirs, 
having a total capacity of 5 1 cubic feet and weighing 4, 340 
pounds. One of these is placed under each seat, running the 
entire length of the car. The others are arranged beneath the 
floor of the car, and all of them rest- on a framework of locomo- 
tive construction supported on the usual type of locomotive 
springs. The framework also supports a heater 7 feet long 
and 19 inches in diameter that contains 500 pounds of hot 
water, through which the air passes on its way to the motors. 

This type of car has run 17 miles on one charge of air, but 
is rated as having a capacity of 12 miles, anything over that 
being reckoned as margin to allow for emergencies, heavy 



580 



COMPRESSED AIR AND ITS APPLICATIONS. 







en O 



3 H 

o S 

O << 

w . 

S >- 



o 



COMPRESSED AIR IN RAILWAY SERVICE. 58 1 

loads, frequent stops, bad tracks, etc. Its normal speed is 12 
miles an hour, but, like the steam locomotive, it can be oper- 
ated at any required speed. 

In Fig. 411 are detailed the proportions of the reheater 
used in the cars of the Metropolitan line, 28th and 29th Streets, 
New York City. It will be seen that the air after pressure 
reduction to the working limit, 150 pounds, is delivered to the 
reheater through a perforated pipe lying on the bottom of the 
cylinder and beneath the hot-water surface. Baffle plates are 
placed across the cylinder to prevent the water from swashing 
on starting and stopping the car. A perforated pipe T along 
the top of the cylinder conveys the air, reheated at the reduced 
pressure, to the throttle valve on the platform and from thence 
to the cylinder. 

In Fig. 412 is shown the elevation and end view of the 
motor gear with an outside cylinder connected directly with the 
crank pin on the wheel. The other wheel is connected by an 
extension of the wheel crank pins and an outside connecting 
rod. The rocker arm g is operated by a link /, pivoted to the 
slide and oscillating on the pivot p, fixed to the frame and also 
connected by a link to the arm/, which is pivoted to the cut-off 
valve at m, and to an extension of the wrist pin on the double 
rocker arm a, which is operated by a sector slide linked to cams 
on the wheel shaft; so that the main valve and cut-off have 
variable motion in both forward and backward running. 

It is apparent from Fig. 413 that the reducing valve is a 
diaphragm valve, specially constructed to deal with high press- 
ure, and that, in addition to the ordinary action of such valves, a 
supplementary action is brought about by reducing the air press- 
ure that is normally kept above the valve head in chamber A. 
In ordinary action this valve graduates air to 150 pounds. 
When it is desired quickly to accelerate under heavy load, a 
movement of the brake-valve handle to a given position dis- 
charges the air from chamber A ; this increases the value of 
the coil spring beneath the diaphragm, opening the reducing 



582 COMPRESSED AIR AND ITS APPLICATIONS. 





COMPRESSED AIR IN RAILWAY SERVICE. 



583 



valve in greater measure, and temporarily increases the working 
pressure to 200 pounds per square inch, while it is desirable to 
use that pressure in the cylinders. 

Fig. 414 illustrates the operation of the air brake of the 




-DETAIL SECTION OF REDUCING VALVE. 



Hardie motor car. The brake piston rod is hollow, and thus 
forms a cylinder within the brake cylinder. 

In the illustration the piston is shown in the set position, 
and the motorman's brake valve would be in service applica^ 



584 



COMPRESSED AIR AND ITS APPLICATIONS. 



tion. Braking force is applied by admitting air to the annular 
space marked R. When release is made the air passes from 
the point T through a by-pass and the release valve to the point 
V in the rear of the piston, and pressure is thus exerted upon 
the greater area of the total diameter of the piston head. The 




Fig. 414.— the brake cylinder. 



difference in pressure area will therefore restore the piston to 
the release position and the air. thus applied in releasing, 
bleeds through the opening 5 and out of the hollow piston 
through numerous ports, W, to atmosphere, the bleeding action 
being so free as to be practically noiseless. 

The first compressed-air locomotive for Iona Island, N. Y., 
to furnish motive power for cars containing ammunition, under 
contract with the United States Government, has been com- 
pleted at the H. K. Porter Locomotive Works. It is the type 
of locomotive decided upon for moving railroad cars about the 
vast magazines which are the storehouses for ammunition used 
in the coast defences and forts throughout the country. The 
engine now finished is a novel one, and was ordered together 
with a complete plant for charging and operating. 

In event of the new locomotive proving a success and 
standing the tests that it will be put to, the Government will 
order a number of others like it, all to be used on the same 
island. Iona Island is probably the greatest storehouse for ex- 
plosives that is owned by the United States. It is situated in 



COMPRESSED AIR IN RAILWAY SERVICE. 



585 



the Hudson River, a short distance from New York, and from 
it ordnance and ammunition are sent out to the various points 
along the coast. For a long time the handling of explosives 
has been done with mules, dragging cars and carts. It has 
been a slow and tedious process, as well as a costly one. The 
island is covered with a series of railroad tracks, and cars from 
the West Shore Railroad are used in shipping material, being 
loaded and moved about by teams. It is absolutely necessary 
that there should be no fire of any kind near the storehouses of 
the ammunition. 

The success that attended the use of compressed-air locomo- 
tives in the great plant of the California Powder Company, near 
San Francisco, drew the attention of the army officials to the 
availability of compressed-air traction for Iona Island, and after 
much planning the first plant was ordered. This consists of 




Fig. 415.— the bardie compressed-air locomotive. 



one locomotive capable of handling standard railroad cars, a 
series of charging stations along the lines of the rails for 
charging the locomotives whenever it is necessary, and a com- 
plete power plant for operating the compressors. 

The new locomotive is said to be one of the largest of its 



586 COMPRESSED AIR AND ITS APPLICATIONS. 

kind ever built. It will run several miles without being re- 
charged, and can be charged with air at any one of the numer- 
ous stations in less than thirty seconds. There being no fire 
of any kind about the locomotives, there is not the least danger 
from explosion. 

THE COST OF COMPRESSED-AIR RAILWAY SERVICE. 

From the few compressed-air railways in which the entire 
plant has been built for a specific amount of service, accurate 
returns of cost of operating as compared with the same service 
of other systems of locomotion have been meagre and un- 
satisfactory. 

The cost of operating the air plant on the Nantes, France, 
railway has been stated at 12 cents per car mile. It is fifty- 
eight miles in length and has gradients of four per cent. 

The cost of operating the air plant on the Berne, Switzer- 
land, tramway has been given as 17 cents per car mile. The 
road is two miles or more in extent and has gradients of over 
five per cent, necessitating heavier power motors than for lower 
grades. 

On the 125th Street line in New York the compressed-air cars 
were switched in between the cable cars and were limited to their 
regular speed, not being favored by conditions for clean runs. 
The frequent stops made necessary by city traffic counted against 
the best conditions for cost of service, and made the volume of 
air used larger than for a less obstructed service. The steepest 
grade on this line is J.J per cent, which for only a short run 
necessitates, as stated for the Berne plant, a heavier motor power 
than for more even grades. The cars actually operated on this 
line were two ; but the installation was made for a larger num- 
ber, which brought the operating cost to an excessive figure, 
viz., 20 cents per car mile. On the basis of a larger number of 
cars, suitable for the compressed-air installation, the cost has 
been estimated at less than 17 cents per car mile. With the 



COMPRESSED AIR IN RAILWAY SERVICE. 



587 



improvements of service now being done the cost should fall 
to about 13 cents per car mile. The average consumption of 
free air per car mile on the 125th Street line has averaged dur- 
ing seven months' service 477 cubic feet per car mile. The 
operation of the air cars on the 28th and 29th Streets line has 
not yet given sufficient data in regard to cost, as the compress- 
ing plant largely exceeds the present needs of the car plant. 

It has been estimated that the actual cost of compressing air 
to 2,500 pounds pressure per square inch, and storing for use in 
a modern air-compressing plant operated with condensing en- 
gines, including coal at $2.75 per ton, water at $1 per 1,000 cubic 
feet, oil and waste, the removal of ashes, labor, repairs, and 
maintenance of power plant, depreciation and interest on cost of 
entire power-plant including buildings, for compressing plants 
of the following capacities, based on the consumption of 2-i- 
pounds of coal per hour per horse power for twenty hours per 
day, will not exceed the following figures: 

Cost per 1,000 cubic feet of free air compressed to 2,500 
pounds pressure per square inch : 





Station capacity. 


Cost. 




Station 


capacity. 


Cost. 


500 


cubic feet per minute. 


..$0.0675 


6,000 


cubic feet per minute 


...$0.0359 


1,000 


" " 


■ • .0571 


7,000 


" 




• • • .0342 


2,000 




. . .0469 


8,000 




" 


. . . .0326 


3,000 


" " 


.0419 


9,000 


" 


" 


... .0312 


4,000 




. . .0394 


10,000 


" 


" 


. . . .0300 


5,000 


11 11 


•• .0375 











Responsible parties will guarantee that the cost will be less 
than stated, and the writer believes that the cost in highest- 
grade plants can be reduced fully 25 per cent, from the above 
figures. 



COMPRESSED AIR FOR UNDERGROUND HAULAGE. 

The use of compressed air for underground haulage was 
probably given its first practical application in the St. Gothard 
tunnel in 1 873 and on, until the tunnel was finished. The initial 
pressure then used was only 210 pounds in the main tank, re- 



588 COMPRESSED AIR AND ITS APPLICATIONS. 

duced to a working pressure of 60 pounds in the secondary 
tank. High pressures had not then entered the realm of the 
practical use of compressed air ; but the early pneumatic loco- 
motives did good work. The modern application of compressed 
air in mine haulage is exemplified in the operation of pneu- 
matic locomotives in the mines of the Susquehanna Coal Com- 
pany at Glen Lyon, Pa., where there are two compressed-air 
motors in operation. The air is supplied by a compressor of 
the three-stage type, having steam cylinders 20x24 inches 
and air cylinders 12^x91 and 5 X24 inches, with water-jackets 
and intercoolers, compressing the air to 600 pounds per square 
inch. The air passes through a line of 5 -inch special strong pipe 
200 feet to the head of the shaft, down the shaft 800 feet, and 
then along the gangway about 3,400 feet, a total length of 4,300 
feet. This pipe line has a capacity of 580 cubic feet and acts 
as a reservoir for the compressor. It is coupled together with 
threaded sockets which are counterbored for a lead filling, which 
is calked. At intervals of about 200 feet, and at all valves and 
charging stations, flange couplings are used with lead gaskets. 
The line is perfectly tight, being tested to 1,500 pounds per 
square inch. Charging stations are placed where required, and 
consist of a universal metallic coupling which is attached to the 
check valve of the locomotive air tanks when a fresh supply of 
air is required. It requires about one and one-half minutes to 
complete the operation of charging the locomotive, and reduces 
the pressure in the main pipe line from 600 pounds per square 
inch to about 570 pounds per square inch. A charge of air 
weighs about 380 pounds. The locomotive is of the four-wheel 
type, having cylinders 7 inches diameter by 14-inch stroke; 
drivers, 24 inches diameter; weight, 18,500 pounds; length 
over all, 17 feet 6 inches; width, 5 feet 2 inches; height, 5 feet. 
The air for propelling the locomotive is stored in two cylin- 
drical steel tanks with a combined capacity of 1 30 cubic feet 
and supported by cast-iron saddles resting on the frames of the 
locomotive. The air flows from the main tanks through a 



COMPRESSED AIR IN RAILWAY SERVICE. 589 

specially designed reducing valve into an auxiliary reservoir, 
and from thence through a throttle valve to the cylinders. The 
pressure in the auxiliary reservoir can be regulated anywhere 
from 30 pounds up to 140 pounds or 150 pounds per square 
inch as required. The air in the auxiliary reservoir is main- 
tained at a constant pressure, while in the main storage tanks 
it may vary from 570 pounds per square inch down to the press- 
ure at which the reducing valve is adjusted ; when this press- 
ure is reached in the main storage tanks the air passes through 
to the cylinders without further reduction in pressure. 

The locomotive hauls sixteen empty cars a distance of 3,700 
feet into the gangway and returns to the shaft sixteen loaded 
cars with one charge of air, starting with a pressure of 575 
pounds per square inch and ending with about 100 pounds per 
square inch. The train of empty cars, including the locomo- 
tive, weighs 60,000 pounds, and the train of loaded cars, in- 
cluding the locomotive, weighs 166,000 pounds. The grades 
favor the loads. The locomotive runs from twenty-five to fifty 
miles per day, depending upon the length of trip and time con- 
sumed in making up the trains at the terminals. This locomo- 
tive was lowered down the mine shaft a vertical distance of 800 
feet without dismantling in any manner. 

PNEUMATIC MINE LOCOMOTIVES OF THE BALDWIN LOCOMOTIVE 

WORKS. 

The new modification of the pneumatic locomotives of this 
company is shown in Figs. 416 to 419, an advance in air- 
motor design in the ribbed compound cylinders. 

Pneumatic locomotives for mine haulage have been in use 
for several years, and are to-day a standard product of all the 
large steam locomotive builders. They possess several features 
which make them ideal for mining purposes and most suitable 
for quite a variety of surface work, generally industrial opera- 
tions, such as plantations, tunnels, powder mills, lumber yards, 



59Q 



COMPRESSED AIR AND ITS APPLICATIONS. 




COMPIH Nl) 1 ' X I- .l.'.M \ I 1C LOCOMOTIVE. 



Six- wheel type. Compound cylinders, ribbed for the absorption of heat from the outer air, 
thus preventing extreme cold in the exhaust. Built for the H. C. Frick Coal Company. 

textile manufactories, cotton mills, storage warehouses, and 
other places where the risk of fire resulting from sparks and 
the freedom from other objectionable features make the com- 



k rfvf 







FIG. 417.— COMPOUND PNEUMATIC LOCOMOTIVE. 

Four-wheel type. Ribbed cylinders. Built for the Philadelphia and Reading Coal and Iron 

Company. 

pressed-air locomotive a most desirable and satisfactory means 
of hauling. 

Compressed-air power has marked advantages over any other 
kind of haulage power for mines and constructive works, where 




FlG. 418.— PNEUMATIC MINE LOCOMOTIVE. 
Two-cylinder, four-wheel type. 



COMPRESSED AIR IN RAILWAY SERVICE. 



591 



the entanglements of electric wires and stays are always in the 
way, and steam is a nuisance. Compressed-air power is a free 
traveller to go wherever a track is laid and even without tracks 




FIG. 419.— SINGLE-TANK PNEUMATIC LOCOMOTIVE. 

Baldwin Locomotive Works. 

in the compressed-air driven truck. The distance run with one 
charge of air is only limited by the capacity of the storage 
tanks, and since high initial pressure has become available, the 
limit of usefulness has been largely extended. 

COMPRESSED-AIR LOCOMOTIVES FOR HAULAGE. 

The mule, which has so long been used for hauling in mines 
and in yard work, has nearly lost his calling by the successful 
adoption of the more powerful agent, compressed air, in the 




FIG. 420.— PNEUMATIC LOCOMOTIVE FOR YARD AND FACTORY SERVICE. 

diminutive narrow-gauge locomotive that needs no feed when 
no work is being done. The compressed-air system has en- 
tirely supplanted steam in underground work, and has become 



592 



COMPRESSED AIR AND ITS APPLICATIONS. 



a most economical competitor of both steam and electricity in 
yard and factory haulage. 

Fig. 421 represents a type of yard locomotive of the H. K. 
Porter Company, Pittsburg, Pa., designed for factory and yard 
work. It is built for narrow gauge and with wheel base 
as short as 3 feet 6 inches, and for curves of 12 feet radius. 
The single air tank carries a maximum pressure of 600 pounds 
per. square inch, with an auxiliary reservoir from which the 
motors are operated at not more than 140 pounds pressure. 
This style of compressed-air locomotive is made in twelve 




INDUSTRIAL 



IEUMATIC LOCOMOTIVE. 



sizes, the smallest having motor cylinders 4x8 inches ; the 
largest, 11x14 inches. 

The larger locomotives built for the longer runs required 
on plantations and for shipping heavy goods from iron works 
and factories are also made in twelve sizes with air-storage ca- 
pacity of from 45 to 260 cubic feet of compressed air at from 
600 to 700 pounds pressure. 



COMPRESSED AIR IN RAILWAY SERVICE. 



593 



COMPRESSED AIR IN RAILWAY SIGNALLING. 



Automatic apparatus operated by compressed air for ringing 
bells at highway crossings are in practical operation. In Fig. 
422 is shown an elevation and plan of the apparatus of the 
Lyman Pneumatic Signal Company of New York. 

A small air-compressing cylinder is located near the rail and 
operated by a lever which 
is depressed by the wheels 
of a passing train, send- 
ing an air impulse 
through an underground 
pipe to a distant crossing 
which makes an electric 
contact that rings a bell. 
A is the lever, 5 a slotted 
cam on a rocking shaft 
B. A train coming in 
one direction swings the 
lever and cam shaft and 
lifts the plate C and the 
connected air piston. A train from the opposite direction only 
depresses the lever in the cam slot and does not give the air im- 
pulse to the signal bell. 

The shortest train repeats the air impulses and furnishes 
sufficient power to close the bell circuit for the required time 
for signalling. Fig. 423 shows the method of arranging the 
position of the air apparatus to the north or south of a crossing. 

The central compressor C is to open the bell circuit and stops 
the ringing by making an air impulse on the piston C (Fig. 
424). Its location should be at the track opposite the signal 
bell. In operation an impulse of air coming through n (Fig. 424) 
lifts the piston in iVand, by means of rod 3, closes the electric 
circuit which rings the bell. The bell rings as long as the 
38 




Fig. 422.— signal air compressor. 



594 



COMPRESSED AIR AND ITS APPLICATIONS. 



piston of N remains up, and this time is governed not only by 
the length of the train that sends the air impulse, but also by the 
fit of the piston and the size of the air escape, which can be 
adjusted for any desired length of time. When the piston in 
C (Fig. 423) is lifted it forces air into the upper ends of iVand 
6* (Fig. 424) and at the same time lifts pins 1 and 2, by which 
valves a and b are opened, exhausting the pressure in the lower 



A 






5 /».-, 



Fig. 423.— the signal station. 

ends of the upper cylinders. The reference letters N, C, and 
5 in (Fig. 424) have the same general meaning as the same let- 
ters in Fig. 423. 

A pneumatic railway switch and signal system has been de- 
vised and put in experimental operation, by which the switches 
and signals are operated from a distant station by means of 
compressed air generated by hand power in the switch station 
in sufficient quantity to operate the local switch and signal 
plant. The system is operated by a double pipe line with slide- 
valve connections operated by levers in the signal tower, which 
by air pressure of about 80 pounds operate pistons in cylinders 
at the switches and signal poles, and thus throw a switch or 
signal to its proper position. The system is very complex in 
its details, which prevents an intelligent illustration here. It 
is in use on the New Jersey Central and other railways. 



COMPRESSED AIR IN RAILWAY SERVICE. 



595 



THE INTERLOCKING SIGNAL AND SWITCH SYSTEM. 



After eighteen years of costly and extensive experimenting, 
the pneumatic interlocking signal and switch system has been 
made a success and a fixture at the leading terminal stations in 
this country. By its aid one man now does the work that 
would otherwise require the combined efforts of six operators, 
and he does the work better, the chances for his making mis- 
takes having been reduced to a minimum. With the lever in 
hand he controls the marvellously efficient interlocking machine, 
which in turn controls a number of 
switches and signals connected by 
pneumatic cylinders. As many as a 
dozen trains may be rushing down 
on the signal-house; one movement 
of his hand — and he has signalled 
them all ; another movement — and he 
has steered each individual train across 
a switch, launching it on its proper 
course. The system in use at the 
Boston Southern station is the largest 
known. There are no less than two 
hundred and thirty-eight pneumatic 
switches in operation ; eleven trains 
may move simultaneously into or out 
of the train-shed; one hundred and 
forty-eight semaphore signals are pro- 
vided for the four hundred possible routes presented in the 
switch system of that terminal. 




Fig. 424.— air pistons under the 
signal bell. 



THE PNEUMATIC BAGGAGE-HANDLER. 



The Grand Rapids & Indiana Railroad has gone one step 
farther by lately adopting the pneumatic "baggage-handler" 
system. This device has proved itself able to handle heavy 



596 



COMPRESSED AIR AND ITS APPLICATIONS. 



baggage much more rapidly than it could otherwise be handled, 
and, moreover, to do away with breakage. The day of the 
baggage-smasher may, therefore, be past. The machine is a 
very simple arrangement of air cylinder and baggage support. 
The latter is lowered to the platform, where it receives the bag- 
gage. Then it rises quickly and is automatically 
swung around by a cam action, carrying the bag- 
gage into the car. The lift is operated by air 
drawn from the train tanks to a special reser- 
voir, and it is controlled by the baggageman 
through suitable cocks on the inside of the car. 
The machine has a lifting capacity of 500 pounds, 
with 70 pounds of air pressure ; it has a spring- 




FlG. 425.— THE PNEUMATIC RAILWAY GATE. 

scale device providing for the weighing of the baggage as it is 
handled, and it is able to load trunks at the rate of six pieces 
every thirty-two seconds. For country stations where now 
there is only one man to handle the baggage, with the usual dis- 
astrous results, this device will save many a trunk from being 
damaged or smashed. 



THE PNEUMATIC RAILWAY GATE. 

Among the many applications of compressed air for operat- 
ing special appliances on railway lines is the pneumatic rail- 
way gate. By this appliance the man in the signal-tower with 
a small hand air-compressor pumps up a pressure sufficient for 
operating the gates, to which the air is transmitted for a consid- 
erable distance by a double-pipe connection with each gate to 
supply compressed air to each side of a piston, to the rod of 
which is attached a chain running over a sheave and up over 



COMPRESSED AIR IN RAILWAY SERVICE. 597 

a sector to which the gate bars are attached. A diaphragm 
piston takes air by a second pipe line to lock the gate at open 
and closed position. The gate is balanced so that the effort of 
opening and closing the gates is very small, and a number of 
gates may be operated at the same time. About forty railways 
in the United States are now operating this system. They 
are built by the Boque & Mills Manufacturing Company, Chi- 
cago, 111. 

THE PNEUMATIC DUMPING-CAR. 

One of the later improvements in railway-car construction 
is the compressed-air dumping-car, made by the Thatcher Car 
and Construction Company, New York City. The body of the 
car being pivoted centrally will dump to either side, or to one 
side only, according to its construction. This is done by means 
of a cylinder mounted on the truck frame, the piston of which 
is coupled direct to the car body; another small cylinder called 
the "latch cylinder," fitted with piston rod and slide valve, 
positively and automatically operates 
the latches which lock the car body 
in its horizontal position, and also 
regulates the air pressure to the 
large or dumping cylinder as re- 
quired, moving its piston up and 
down, thus dumping the load and 
returning the body to its horizontal 
position and locking it. An inde- FIG . 426 .~the pneumatic dump- 
pendent reservoir which each car car- 
ries contains an ample supply of air for operating the dumping 
cylinder, and is charged by the engineer through a train pipe 
used for the air brakes at times when the air brake is not in 
use. The pressure is held in the receiver by a check valve, so 
that the action of the air brakes is not interfered with. 




598 COMPRESSED AIR AND ITS APPLICATIONS. 

THE PNEUMATIC TELEGRAPH. 

For local purposes and short distances, so as to connect dif- 
ferent parts of buildings, factories, etc., the pneumatic or air- 
pressure telegraph has of late been successfully introduced. 
The pneumatic telegraph is operated by compressing a quantity 
of air in a rubber receptacle and forcing the same through the 
connecting pipes to act on a second distant receptacle that is 
held compressed when in a state of rest. The expansion of 
this second receptacle actuates a bell or other signalling appa- 
ratus. The apparatus is, however, not applicable to greater dis- 
tances, as the volume of air in the communicating pipes is too 
large to be compressed with considerable power by the pressure 
exerted by the first receptacle, especially as such pipe connec- 
tions cannot be kept tight enough to prevent the escape of air. 
The Italian engineer Guattari has overcome in a simple and in- 
genious manner some of the difficulties of these telegraphs, by 
substituting, in place of a few powerful compressions, a quick 
succession of alternating compressions and dilatations, which 
produce, so to say, an oscillating motion of the air in the pipes. 

THE AIR BRAKE AND ITS WORK. 

The air brake dates its practical inception from the year 
1869, in the "straight air brake" system of George Westing- 
house, Jr. 

This consisted of a pump operated by steam from the loco- 
motive boiler, which compressed air into a reservoir conveniently 
located about the engine. This was under the control of the 
engineer by means of a valve in a pipe leading from the reservoir. 
From this valve a pipe extended under the tender and was 
attached by flexible hose connections to a similar pipe under the 
entire length of each car. Branch pipes led to " brake cylinders, " 
and the rods of the pistons in the latter were connected with 
the brake levers on the cars. By placing the brake-valve 
handle in such a position that the reservoir on the engine was 



COMPRESSED AIR IN RAILWAY SERVICE. 



599 



connected with the train line under the cars, air pressure passed 
to these cylinders, pushing the pistons outward, operating the 
brake-levers, and forcing the brake-shoes against the wheels. 
It was found that the operation of this apparatus was too slow, 
dangerous when used on long trains, and did not meet require- 
ments. 

About 1872 or 1873 Westinghouse produced a "plain auto- 
matic brake " which embodied the addition of an auxiliary 
reservoir and a triple valve to each vehicle. Each reservoir was 
of a capacity sufficient to provide an amount of compressed 
air to supply the power for the car on which it was placed. 






TO AUXILIARY 




TO CYLINDER 



TO TRAIN LINE 



Fig. 427.— plain triple valve. 
Showing service position. 



The operation of this brake was radically different from that of 
the " straight air brake." In the former the compressed air was 
stored in the main reservoir until required for the application 
of brakes ; in the latter the main and auxiliary reservoirs and 
train pipe were always charged with compressed air at working 
pressure, to prevent the application of the brakes. The former 
system was operated by pressure from the main reservoir; the 
latter system was operated by a reduction of pressure in the 
train pipe, which reduction caused the triple valve automatically 
to assume a position that would permit the pressure stored in 
the car reservoir to flow through the triple valve into the brake 
cylinder. It was automatic in action in case of accident, such 
as the bursting of hose or the train breaking in two, but like the 



6<DO COMPRESSED AIR AND ITS APPLICATIONS. 

"straight air brake " was not found to be capable of successful 
operation on long trains of freight cars. 

In 1885 the Railway Master Car-Builders' Association ar- 
ranged for a series of experiments. Several companies entered 
into the competition, but none succeeded in stopping long 
trains of freight cars without violent and disastrous shocks. 
The trials were renewed in 1887, with five competing com- 
panies. The report of the committee was against all the com- 
peting devices, the committee concluding that air brakes actu- 
ated by electricity were the only ones likely to be capable of 
successful operation on long trains of freight cars. 

After these trials Mr. Westinghouse set himself to work to 
obviate the difficulties that had not yet been overcome, namely, 
to provide for practically instantaneous application of the brakes 
throughout a train, and to prevent shocks to the cars. 

In the latter part of 1887 he succeeded in constructing a 
quick-action automatic brake, capable of being successfully ap- 
plied to a train of fifty or more cars, and operative under all con- 
ditions of practical railway service. The requirements with 
which he then for the first time successfully complied were: 1. 
The regulation of the force to be applied to the brake-shoes so as 
to secure all necessary graduations, from the mere slackening of 
speed to the service-stop, and from the service-stop to the 
emergency-stop. 2. The automatic operation of the brakes in 
case of accident. 3. The practically simultaneous operation of 
the brakes on each car, so that, in long trains of freight cars, 
shocks might be avoided. 4. The control of all these opera- 
tions by the engineer. 5. Certainty of operation under all con- 
ditions. This was found to be the first system which practi- 
cally solved the problem of quickly stopping a long freight train 
in time of danger, and, if desired, also permitted of a gradual 
application. 

Plate A illustrates the relation and general management of 
the parts of the air-brake equipment on an engine, tender, and 
passenger car. The tender equipment shows the " plain triple " 



■ ~ - -'- ■ m 




Plate A.~thi wi ■ n ,.h 



COMPRESSED AIR IN RAILWAY SERVICE. 



60 ] 



valve used on engines and tenders, while the triple valve shown 
on the car equipment is the '"quick-action" type. The main 
reservoir is carried beneath the engine and is charged with air 
from a pump also on the engine, the pump being operated 
by steam from the boiler. The " engineer's brake and equaliz- 
ing discharge valve " is located in the cab of the engine and is 
connected to a pipe leading from the main reservoir and a second 
pipe communicating with the train pipe. This valve, under the 
control of the engineer, regulates the flow of air from the main 



to A=owuvmy 



< TO CYLI.NDIB 




•TO TRAIN LINE 



Fig. 428.— quick-action triple valve. 
Showing release position. 

reservoir into the train pipe for releasing the brakes, and charg- 
ing the auxiliary reservoirs, and from the train or brake pipe to 
the atmosphere for applying the brakes. The train pipe leads 
beneath all the cars of a train, being connected between the 
cars by flexible hose coupled to the pipe sections. By means 
of an angle-cock at each end of the pipe of each car, such pipe is 
closed before separating the couplings, thus preventing the es- 
cape of air and the application of the brakes when the cars are 
uncoupled. 

Beneath each car is an auxiliary reservoir which takes a 
supply of air from the main reservoir, through the train pipe, 



602 



COMPRESSED AIR AND ITS APPLICATIONS. 



and stores it for use on its own car. The brake cylinder, by 
a suitable pipe, is connected to the triple valve, and its piston 
rod is attached to the brake levers in such a manner that, when 
the piston is forced out by the air pressure, the brakes are applied. 
The " quick-action " automatic triple valve is connected to the 




Fig. 429.— quick-action triple valve. 
Showing release position. 

main train pipe, auxiliary reservoir, and brake cylinder, and 
as its name implies, it, in response to variations of train-pipe 
pressure, performs three functions in the operation of the, 
brake : applies the brake, releases it, and charges the auxiliary 
reservoir. When a reduction of air pressure is made in the 
train pipe, the auxiliary reservoir pressure, which is then 



COMPRESSED AIR IN RAILWAY SERVICE. 603 

greater, forces the triple piston, and it in turn moves the slide 
valve, to a position such that a port connection is made permit- 
ting air to flow from the auxiliary reservoir to the brake cylin- 
der. If when the brake is applied the engineer permits press- 
ure from the main reservoir on the engine to enter the train 
pipe, its pressure is raised to an amount in excess of that in 
the auxiliary reservoir. With the train-pipe pressure greater 
than that in the auxiliary reservoir, the triple piston and slide 
valve are forced back to what is known as release position, in 
which position a port in the slide valve permits brake-cylinder 
pressure to escape to the atmosphere, and a small port, known 
as the feed port, connects the two sides of the triple piston, 
thus recharging the auxiliary reservoir from the train pipe in 
anticipation of a future use of the brake. 

The quick-action triple differs from the plain triple Fig. 427 in 
that it has supplemental valves which, in case of a sudden reduc- 
tion, made by the engineer, by the train parting, or otherwise, 
the brakes are not only applied more quickly, but are applied 
with greater force due to the supplemental valves unseating, 
thus allowing a portion of the train -pipe pressure to reach the 
brake cylinder. The air taken from the train pipe on the first 
car by the supplemental valves, in an emergency application, 
causes a sudden reduction which throws the next triple into 
quick action, this one the next, and so on throughout the train, 
the brakes applying with such rapidity that, with a fifty-car 
train, the fiftieth brake will start to apply inside of two and 
one-half seconds. 

PARTS IN THE FOLDING PLATE, A. 

Auxiliary Reservoir. — A reservoir, one of which is located 
under each vehicle, in which air is stored for the purpose of 
furnishing braking power for the vehicle upon which it is 
located. 

Brake Cylinder. — That part of the brake system in which 
the piston, actuated by compressed air when the brake is ap- 



604 COMPRESSED AIR AND ITS APPLICATIONS. 

plied, is located. The piston, acting upon a system of levers, 
draws the brake shoes against the wheels, thus producing the 
retarding power which tends to stop the rotation of the wheels. 

Triple Valve. — A valve, one of which is located upon 
each vehicle equipped with an air brake. It derives its name 
from the three functions it automatically performs in response 
to variations of train pipe and auxiliary reservoir pressures; 
it automatically charges the auxiliary reservoir, applies, and 
releases the brake. 

Stop-Cock. — A valve by means of which the brake on any 
vehicle may be cut in or out. With each equipment, it is found 
in the pipe which connects the main train pipe with the triple 
valve. 

Car Drain Cup. — A cast-iron cup in which is placed a 
piece of perforated brass ; it acts as a strainer to prohibit the 
passage of any foreign substance from the main train pipe into 
the triple valve. 

Angle Cock. — A valve, one of which is located at either 
end of every vehicle. The handle may be turned so that the 
valve will permit air to pass through into the train pipe beyond, 
or so as to stop the flow of air by the point at which it is located. 

Hose. — A flexible connection which, with the cast-iron 
coupling, furnishes a means of connecting the train pipe on one 
vehicle with that on the adjoining one. In case the train pulls 
apart the couplings separate, thus permitting of a discharge of 
air from the train pipe which causes the brakes to apply. 

Conductor's Valve. — A valve having a pipe connection to 
the main train pipe, and so located in baggage, mail, and pas- 
senger cars that it is easily accessible to the occupants ; by turn- 
ing the handle of the valve a sudden discharge of air is made 
from the train pipe, thus causing a rapid application of the 
brakes throughout the train. 

Engineer's Brake Valve. — A valve, located within con- 
venient reach of the engineer, by means of which he is enabled 
to control the amount of train-pipe pressure carried, the ap- 



COMPRESSED AIR IN RAILWAY SERVICE. 605 

plication and release of the brakes, also the recharging of the 
brake system. 

Brake- Valve Reservoir. — Usually located beneath the 
cab foot-boards, it furnishes a considerable volume of air above 
the equalizing piston of the brake valve ; this volume permits 
the engineer to make a gradual reduction of pressure above the 
piston, in response to which it rises gradually, thus allowing 
train-pipe pressure to escape at the "train line exhaust," com- 
paratively slowly. A slow reduction causes a gradual application 
of the brakes, as in station stops ; a quick reduction causes a 
quick application of the brakes, such as is used in cases of im- 
minent danger. 

Pump Governor. — The part shown just to the left of the 
pump. It is designed to shut off the steam supply to the pump 
when a predetermined air pressure has been obtained. 

Air Pump. — It is shown at the extreme right of Plate A. 
The top or steam piston actuates the lower or air piston, which 
latter compresses air on one side, while on the other, air at 
atmospheric pressure is being drawn in. The air compressed 
lifts one of the discharge valves and passes on to the main 
reservoir, from which point it passes through the brake valve 
into the brake system at the discretion of the engineer. 

Main Reservoir. — The one usually placed upon the en- 
gine, in which a large supply of air is stored for the purpose of 
releasing the brakes and recharging the brake system when so 
desired. Air for the signal system is also taken from the main 
reservoir. 

Westinghouse Air-Signal Equipment. 

The compressed-air train air-signalling apparatus has be- 
come one of the indispensable conveniences in passenger rail- 
way service. 

It consists of a pipe extending from the main reservoir on 
the engine to a reducing valve (Fig. 430) which reduces the 
main reservoir pressure to 40 pounds, the amount used in the 



6o6 



COMPRESSED AIR AND ITS APPLICATIONS. 



signal system. From the reducing valve the air flows to a tee, 
one branch of which leads to the signal valve (Fig. 431), and 
the other to a separate pipe which passes back to the end of 
the train. On each car is placed a discharge valve to which a 
cord, running the full length of each car, is attached. 

The pressure in chambers A and B (Fig. 431) equalizes, be- 
ing connected by a slightly loose fit of stem 10 in bushing 9. 
In response to the reduction of signal-line pressure, made when 
the discharge valve on a car is opened, a reduction wave 




Fig. 430.- signal reducing valve. 

is carried to the signal valve, where it first manifests itself in 
chamber A. The greater pressure in chamber B raises the 
diaphragm 12 and stem 10, thus unseating the valve at the end 
of stem 10, and air escapes at X through a pipe leading to a 
small whistle, located conveniently close to the engineer, caus- 
ing it to blow. 

This same reduction wave causes the reducing valve to open, 
and the air from the main reservoir entering the signal line 
causes the pressure in chamber A (Fig. 431) to increase and 



COMPRESSED AIR IN RAILWAY SERVICE. 



607 



force the diaphragm down again, closing the valve at the end 
of stem 10. It is then only necessary to wait two or three 
seconds to allow the pressure to equalize throughout the signal 
system, when another signal may be given. 



AIR BRAKES FOR TROLLEY CARS. 

Compressed air is largely in use for air brakes on trolley 
and cable cars, the air being compressed by direct connection 
from the piston to a cam on the axle, by a reducing gear from 




x ^to whistle 

Fig. 431. -signal valve. 

the axle, or by an electric motor when available. This system 
has been placed on many of the trolley roads in the United 
States and in Europe by the Standard Air Brake Company of 
New York. 

In operating brake mechanism by compressed air obtained 
through the action of their air-compressor operated from the axle 
of the car, it is necessary to stop the compressor's action when the 
air has been compressed to a predetermined limit, in order that 
the compressor may continue to run with the axle but without 
absorbing power. This is accomplished as follows : as long as 
the air has not reached the set pressure to be carried, the com- 



608 COMPRESSED AIR AND ITS APPLICATIONS. 

pressor forces air through the discharge valve direct to the 
reservoir, and will continue so to do until the required pressure 
is reached. The pressure will then open a regulator valve and 
admit air under a diaphragm, forcing upward the governing 
piston and lifting the suction valve from its seat. 

This allows the compressor piston to move freely, and pre- 
vents it from doing any work until, by application of the air to 
a brake-cylinder, the pressure is reduced. 

The reduction of pressure, acting upon the regulator, re- 
leases the air confined under the diaphragm, and allows the 
governing piston to fall, reseats the valve, and the compressor 
resumes furnishing pressure. 

In making a stop, only two or three pounds of registered air 
pressure is required. This the compressor furnishes in a very 
short travel of car. The reservoirs hold in reserve several 
times the amount of air required to stop the car, even without 
additional supply. The air pressure is thus practically inex- 
haustible under the conditions of operation. 

When the direct or geared axle-driven compressor is used, 
enough compressed air is automatically maintained in the reser- 
voir to admit of frequent stops. 

The electric compressor does not depend upon the car axle; 
it is entirely disconnected therefrom. The motor is operated 
by the trolley current only when necessary to maintain proper 
pressure in the storage reservoir. All the working parts of 
these compressors are enclosed. It is only necessary to lubri- 
cate regularly. The construction resembles that of the modern 
enclosed motor in that slush, water, and dirt are excluded. 

The electric compressor acts substantially similar to the 
other, in so far as relates to the regulating of reservoir press- 
ure. The automatic current controller, however, puts the elec- 
tric compressor in or out of service, according as the air supply 
in the reservoir increases or diminishes. 

The electric compressor may be placed anywhere on a car, 
under, inside, or outside. 



COMPRESSED AIR IN RAILWAY SERVICE. 



609 



THE LOCOMOTIVE BELL-RINGER. 



If you wish to hear locomotive bells rung by compressed air, 
you must take a train on the Kansas City, St. Joseph & Council 
Bluffs Railway, on which line a number of pneumatic bell- 
ringers are in operation, giving admirable results. 




Fig. 432.— pneumatic bell-ringer. 



It is attached to the air-pump receiver on a locomotive, and 
by the automatic vibration of the air piston it operates the bell 
crank and rings the bell. 



Chapter XXVII. 



PNEUMATIC WORK 



PNEUMATIC WORK. 



PNEUMATIC SHEEP-SHEARING. 

Many attempts to perfect a mechanical device which would 
lighten the work for the shearer, prevent the wool from being 
injured by second cuts, and guarantee the next fleece to be even 
in length, or "wool-topped," 
have in the past, twenty years 
been made. But it was only 
when the " Australian Shear- 
er " made its appearance that 
the wool-growers and shear- 
ers gave the hand-shearing 
entirely up. 

In Fig. 433 is represented 
an English compressed-air 

sheep-shearing machine. A small piston vibrates and operates 
the cutters through a lever with a diagonal slot in which a pin 
in the piston-rod head slides. An arm on the piston rod operates 
the valves at the end of each stroke. 

The Australian sheep-shearing machine (Fig. 434) is exceed- 
ingly simple, direct-acting, and easy to handle. It is composed 




Fig. 433.— sheep-shearer. 




PlG. 434.— AUSTRALIAN SHEEP-SHEARER. 



of eight pieces : The body of the shearer, the oscillating fork, 
the piston, the valve, the comb, the cutter, the piston covers, 



6 14 COMPRESSED AIR AND ITS APPLICATIONS. 

and the tightening ratchet. The valve is entirely balanced. 
The motion of the machine, similar to that of a rock drill, is 
given by the piston, which is if-inch diameter, -f-inch stroke. 
The fork is centred on a half-round bearing, the cup of which 
forms an oil receptacle, so that the bearing is all the time 
working in a bath of oil, reducing the friction. The pressure- 
nut, which regulates the pressure of the cutter on the comb, is 
inside of the body of the machine, so that it cannot interfere 
with or tear the fleece during work. The machine having no 
perceptible vibration, as can be proved by laying it down on 
the floor while running at full speed, the wrist of the operator 
is not subjected to any strain. The weight of the machine is 2 
pounds 2 ounces, and this being counterbalanced, the shearer 
has neither strain nor weight to overcome. The motive power 
is air under a pressure of about 40 pounds to the square inch, 
which is conveyed to the machine through a rubber tube \ inch 
in diameter. Each machine uses 15 cubic feet free air per 
minute. The absence of joints and complications permits the 
shearer to work in any position he desires. The machine 
makes 6,000 oscillations per minute, but does not run hot, as 
the exhausted compressed air passes through the hollow casing 
of the body and escapes over the cutter, keeping the fleece well 
before the points of the comb, enabling the shearer to watch 
the operation, and at the same time keeping the machine cool 
while in his hands. 

The inconvenience of the heat and the disadvantage of the 
friction which causes the heat and increases the wear and tear, 
involving cost of repairs and fear of delay at shearing time, are 
thus obviated. The simplicity of the construction dispenses 
with the necessity of skilled labor in setting up, adjusting, or 
running the machine. 

The use of this machine reduces the time of shearing from 
an average of 70 sheep by hand to about 100 per day of ten 
hours. At Barsham, in Australia, three men sheared 334 sheep 
with this machine in ten hours, the third day they ever handled 



PNEUMATIC WORK. 6l$ 

machines. Furthermore, the " Australian Shearer " saves about 
three-quarters of a pound of fleece wool per sheep, a profit of 
about 16 cents; and as the wool is worth 1 cent a pound more 
when cut in this way, as it is longer and more uniform in 
length, than by hand shearing, this would, with an average 
yield per sheep of about 8 pounds of wool, bring the total profit 
by the use of this method up to 
24 cents per sheep. 

Another point in favor of this 
machine is that by its use the 
animals are never mutilated. 

They are made by Rochet & 
Company, Paris, France. 

COMPRESSED AIR IN A SAW-MILL. 

The power that operates a 
saw-mill, be it steam or water, is 
utilized for compressing air to 
operate the various saw-mill ap- 
pliances that both steam and water are unfitted for, from the 
trouble of condensing steam in interrupted use and the liability 
of water to freeze in cold weather. The log-flipper for roll- 
ing logs out of the log slide, shown in Fig. 435, and the 
nigger for rolling and turning logs on the saw-carriage (Fig. 
436) are some of the new uses for compressed air. These de- 
vices, together with a jump saw for cutting logs to the proper 
length, and a saw-feed motor, all driven by compressed air, are 
in successful operation at the Engel Saw-Mill, Orono, Me. 



COMPRESSED AIR IN BASKET-MAKING. 

Take the work of basket-making. Surely, no one ever heard 
of any of the old machines turning out 180 bushel-baskets per 
hour, or 1,800 baskets per day, but a compressed-air basket- 
making machine is now doing it at the Michigan Avenue fac- 




FlG. 435.— LOG FLIPPER. 



6i6 



COMPRESSED AIR AND ITS APPLICATIONS. 



tory, Traverse City, Mich. The staves of the baskets are fast- 
ened to the hoops by staples of wire taken from the coil, joined 
and driven by the machine. The staves radiate from a centre 
in a disc-like shape. To bend them into the lines of the bas- 
ket form, four processes or movements are made by the ma- 
chine, all of which are automatic and obtained by the medium 

of compressed air. The 
whole combination is very 
simple. The air is not 
cooled, and the machine 
runs ten hours every 
working day. 

THE AIR-BRUSH. 

Then there is the foun- 
tain air-brush, which 
some claim will soon be 
adopted by the leading 
artists for applying color 
on canvas. It is shaped 
like and is but little lar- 
ger than a lead pencil, is 
handled in the same man- 
ner, applies color in large quantities in a short time, and is 
yet adjustable for the finest line ever drawn on canvas by a 
gifted artist. 




Fig. 436.— pneumatic nigger. 



COMPRESSED AIR FOR BLOWING YACHT AND LAUNCH WHISTLES. 

To the water sportsman there is nothing more pleasing than 
a well-toned air-whistle for signalling. The push and draw 
whistle, at the hand of the wheelman, by intelligent manipu- 
lation can be made not only to give the ordinary signals for 
navigation, but can be operated telegraphically for other com- 
munications. 



PNEUMATIC WORK. 



617 



A small air tank under the forward deck may be charged 
by an air pump operated by the propelling engine, and will store 
air sufficient for operating the whistle when the boat is not 




Fig. 437.— push whistle. 



Fig. 438.— pull whistle. 



running. They are furnished by the Gleason-Peters Air-Pump 
Company, New York City. 



COMPRESSED AIR FOR BLOWING FOG SIGNALS. 

The United States Lighthouse Department has for some 
time devoted much attention to the improvement of its fog sig- 
nals, and to that end has recently adopted compressed air in 
place of steam for sounding fog signals. A very compact plant 
has been developed for this ser- 
vice, and one is now installed 
at Montauk Point, on the ex- 
treme eastern end of Long 
Island. The motive power is 
furnished by a ten-horse-power 
Hornsby-Akroyd oil engine, 
which drives an Ingersoll-Ser- 
geant Class E air compressor. The oil engine occupies a floor 
space of 9 feet 2 inches by 5 feet. The air compressor has a base 
measuring 6 feet by 2 feet 1 inch, and is capable of furnishing 



."HI 




Fig. 439.— air tank and whistle. 



6l8 COMPRESSED AIR AND ITS APPLICATIONS. 

107 cubic feet of free air per minute at 150 revolutions. The 
air is compressed and delivered to a receiver at 50 pounds press- 
ure. It is then carried to another receiver about 200 feet dis- 
tant. Midway on the pipe line a reducing 
valve regulates the pressure and admits it to 
the second receiver at 30 pounds pressure. 
This receiver holds the immediate supply of 
air to operate the trumpet. 

Exhausting through the siren at this lower 
pressure enables the receiver to maintain the 
supply after a fog rises for a time sufficient to 
get the engine and compressor in operation. 
There are two trumpets attached to the re- 
ceiver, which are used together or alternately, 
as desired. A first-class siren is supposed to 
consume 12 cubic feet of free air per second. 

The siren is sounded automatically, and 
blows at intervals of 30 to 50 seconds. As a 
musical instrument it can be best described 
by calling it a big clarionet. 

The Daboll trumpet is another fog signal 
similar in general design, but having a smaller 
range of audibility, and requiring less power. 
The plant used consists of a four horse-power 
engine and a vertical belt-driven compressor 
furnishing 17 to 20 cubic feet of free air per 
minute. It delivers air at a pressure of from 
5 to 10 pounds to a receiver which supplies the 
trumpet. 

Fig. 440.— siren. . 

The importance of conveying sound or a 
signal to a greater distance than heretofore in a fog or in thick 
weather at night, has long been felt, and at last the want has 
been met in the production of the " Brown " fog-horn or siren, 
which is illustrated in Fig. 440. It consists of a chamber con- 
taining a peculiar mechanism for producing a large volume of 



PNEUMATIC WORK. 619 

sound in the vibration of the air passing the mechanism, and 
which is still further strengthened by the immense trumpet that 
surmounts the chamber. It seems to fulfil all the conditions 
required on shipboard, at lighthouses, and on lightships. It has 
been heard a distance of 31 miles on the open ocean. It re- 
quires about 80 pounds pressure for its best work. When steam 
is used, a drip pipe is inserted in the chamber to drain off any 
water that may be condensed in the apparatus by leakage of 
steam through the valve. On the lightship off Sandy Hook, 
New York harbor, the air is compressed by a kerosene engine 
and stored in receivers for ready use in the siren. 

COMPRESSED AIR FOR RAISING SUNKEN VESSELS. 

The use of air pumped beneath the sealed decks of sunken 
vessels for raising them has been in successful practice for 




-THE AIR-CASK SYSTEM. 



many years. Casks or bags placed on the inside or fastened to 
the outside, and inflated by pumping air into them, has been 
the means of saving many vessels that otherwise would have 
been a total loss. Long iron tanks have been floated to the 
sides of a sunken vessel and filled with water sufficient to sink 
them., when they are attached to the side of the vessel and air 
pumped in to displace the water. The buoyancy of the air 
tanks raised the vessel to or near the surface for towage to a 
shelter. By placing the air-bags under the deck, the schooner 
Glenoid was raised in Great South Bay, also a vessel in Puget 



620 



COMPRESSED AIR AND ITS APPLICATIONS. 



Sound. Failures have been made by filling the bags or casks 
with too much air, which expands in rising from deep water 
and bursts its enclosure. Air vents at the bottom of each bag 
or cask are safety-valves for deep-water work by compressed air. 
The bursting of the air bags has been the cause of failure in 
the early work of raising vessels by compressed air. Colonel 
Gowan met this difficulty in the attempt to raise the United 
States steamer Missouri at Gibraltar in 1845. He tried it at 




I 

Fig. 442.— the air-bag system. 



Sebastopol, but failed at first. A combination of floats and 
compressed air finally made a success in raising nearly one 
hundred vessels. 

Fig. 442 represents Captain Austin's plan, in which the large 
inflatable canvas bags, h, h, h, in the cut, were rendered water 
and air proof by india-rubber and strengthened by envelopes of 
netting. Chains were swept under the vessel and fastened to 
horizontal chains to which the air bags were lashed. Air was 
pumped in through the air pipes, i, i, i, allowing for sufficient 
expansion of the air as the vessel rose. 

Compressed air played a most important part in the raising 



PNEUMATIC WORK. 621 

and floating of the steamer Plymouth from the rocks in the har- 
bor of Newport, R. I. The steamer had double hulls with 
compartments between the hulls, which were ruptured by the 
vessel running upon the rocks, and many of the partitions be- 
tween the compartments were injured so as to cause leakage 
into a large portion of the space between the hulls. 

It was found that the pontoons and derricks could not lift 
the vessel sufficiently to clear the rocks, and recourse was had 
to pumping air into the compartments by a compressor utilized 
for the purpose, which forced the air throughout the compart- 
ments through the drainage-pump pipes and thus added about 
400 tons to the lifting power of the derricks and pontoons. It 
was found after floating the steamer that the air compressor 
was able to keep her afloat without the pontoons and derricks, 
which were then unshipped and the vessel was towed up to 
Newport. 

COMPRESSED AIR IN SUBMARINE EXPLORATION. 

There is no condition of the relation of compressed air to 
human vitality more delicate and important than when a man 
dressed in a diver's close-fitting armor descends to the bottom 
of the sea. 

The sudden change of atmospheric effect upon his system 
by great pressure in descent, and its release in ascent, calls for 
great caution as to the time required for the change in press- 
ure, as well as an experienced practice by degrees in depth, 
combined with a strong vitality in the person, before excessive 
depths can be accomplished and work performed. The least 
mishap may be fatal, yet there are men who have practised this 
work for many years without accident or material deterioration 
in health. 

The usual work of the diver is under 100 feet in depth; 
seldom 150 feet; and the greatest depth that has ever been 
reached by a diver is 204 feet, requiring an air pressure of 
88-^ pounds to balance the water pressure. 



62 2 



COMPRESSED AIR AND ITS APPLICATIONS. 



The armor consists of a helmet to protect the head ; a dress, 
of canvas and rubber, attached to the helmet; shoes, with lead 
soles, to keep the feet down and the body upright ; lead weights 
to sink the diver to the bottom, and to prevent his rising- from 
an over-pressure of air from the air-pump. A life or signal' 
line is used for lowering and raising the diver, and for the trans- 
mission of signals between the diver and his attendant. 




Fig. 443.— submarine exploration. 



The diver, being dressed in his flannels, is now equipped 
with his dress ; the air-hose is screwed to the helmet and air- 
pump, the pump started and the headpiece screwed on, and he 
is lowered to the bottom, where he can remain from one to six 
hours, according to the depth of water, the speed of the tide, 
and the character of the work. 

The helmet is the most important individual piece in the 



PNEUMATIC WORK. 



623 



outfit, for to it is attached the regulating valve seen at the right 
side ,of the helmet in Fig. 444, and in reach of the diver's 
hand, allowing him to adjust the escape of air to suit the needs 
of respiration, irrespective of the automatic air escape. 




Fig. 444.— the diver in armor. 



This helmet has the latest improvements in the addition of 
the top glass that the diver may look upward without throwing 
the body back. A telephone attached to the helmet is a late 
and important addition to the facilities for operating in sub- 



624 COMPRESSED AIR AND ITS APPLICATIONS. 

marine work. A transmitter and receiver are fixed on the inside 
of the helmet and connected by insulated wires with their coun- 
terpart in the hands of the attendant, by which orders and in- 
formation may be quickly passed, which has been a most tedi- 
ous process under the old jerk-cord system. 

The amount of free air required by a diver varies somewhat 
under the varying pressure in which he is operating and of 
habit in respiration. And as a man in normal condition makes 

about 1 6 respirations per 
minute with an average of 
40 cubic inches at each 
respiration, it will require 
nearly half a cubic foot of 
free air per minute for 
respiration alone, and for 
exhausting the vapors from 
the body as much more, 
or, say, a cubic foot per 
minute. 

In Fig. 446 is illustrated 
a submarine air-pump, 
double-acting, single cylin- 
der, of capacity for one 
diver at ordinary depths, and to 100 feet water pressure. It is 
furnished with a water cistern for cooling the compressed air, 
and a pressure gauge. 

The above submarine apparatus is manufactured by A. J. 
Morse & Son, Boston, Mass. Their catalogue contains inter- 
esting details in regard to management in the use of submarine 
armor, habits and living of divers, and their health. 




Fig. 445.— the helmet. 



COMPRESSED AIR FOR DREDGING CHANNELS. 

Dredging experiments have been made, especially in Eng- 
land, Holland, and the United States, with apparatus designed 
for digging up alluvium, dissolving in water the materials of 



PNEUMATIC WORK. 



625 



which it consists, and giving these up to natural currents when 
the latter have their greatest strength. Such experiments, 
however, have not given satisfactory results, since the materials 
thus dredged were lifted but to a small distance from the bot- 
tom from which they had been extracted, and thus almost im- 
mediately settled back again in the same place. Although this 




Fig. 446.— single-cylinder double-acting air pump. 



<aode of dredging had therefore to be given up, it has been suc- 
cessfully taken up by Mr. Meinesz, who employs compressed 
air for forcing to the surface the material that has been de- 
tached by means of a kind of harrow, in order to put it thus in 
contact with as great a number of molecules of water as possi- 
ble and to give it a velocity in a direction opposite that of grav- 
40 



626 COMPRESSED AIR AND ITS APPLICATIONS. 

ity. Once raised to the surface of the water, the sands are 
carried off by the current to distances which vary according to 
the swiftness of the current and to the depth from which they 
have been dredged. The whole question, then, resolves itself 
into a study of the direction and force of the current, so that 
the deposits shall be borne away as far as possible from the 
channel that it is desired to excavate. 

A late innovation upon the old system of operating the 
clam-shell bucket by chains, has been made by substituting a 
cylinder and piston moved by compressed air for opening and 
closing the bucket ; the action being wholly independent of the 
hoisting chains and of the position of the bucket. The hose 
for operating the piston is wound on a counterbalanced reel 
and is carried freely by the movement of the bucket. 

The advantages claimed are a wider scope to the action of 
the bucket and the utilization of the full weight of the bucket 
and air cylinder to produce a full-depth scoop of the bucket, 
which in the old way was lessened by the pull of the bucket- 
closing chain. 



Chapter XXVIII. 



PNEUMATIC WORK— Continued 




PNEUMATIC WORK. 

{Continued.) 
THE COMPRESSED-AIR BLAST. 

An interesting application of the use of compressed air is 
that of the Fallbrook Railway Shops in furnishing a blast for the 
boiler-makers' forges. The driving rig was removed from an 
ordinary portable forge (Fig. 
447), and the nozzle B was 
screwed in the shell so that the 
air current would impinge on 
the vanes of the fan A. The 
amount of throttle opening re- 
quired is very small to drive 
the fan at a high rate of speed, 
so that it is remarkably eco- 
nomical of air. The blast fur- 
nished is almost an ideal one for this purpose, and one capable 
of the closest regulation. 

By the device illustrated in Fig. 447 the compressed air sup- 
plies a blast of many times its own volume, and with all the 
pressure required. 

The compressed-air injector is illustrated in Fig. 448. The 
fact is well known that the principle of action of the steam in- 
jector and ejector may be applied to air for forcing a larger 
volume at a less pressure into a receiver for any use, and espe- 
cially for ventilation. 

Experiments have shown that one volume of air when 
passed through a nozzle as at C (Fig. 448)5- when the apparatus 
is arranged as an injector, at a pressure of 5 pounds per square 
inch, will induce 30 volumes of free air as measured by a 
meter. Air under pressure will discharge through a nozzle of 



Fig. 447.— induced air blast. 



630 



COMPRESSED AIR AND ITS APPLICATIONS. 



best form at a velocity of about 650 feet per second; it is easy 
to understand that free air will be induced and discharged with 
it into a secondary receiver. Such an arrangement is shown 
in the cut (Fig. 448), in which B is the receiver, D the induced 
current nozzle, A C the compressed-air nozzle, E the air cham- 
ber, and Fa, light check and free-air inlet. 

This air injector has been tried with success, though the 
experiments have not gone far enough to determine to what 
extent it will effect a saving in the production of pneumatic 




Fig. 448.— the compressed-air injector. 

power. It has been found that with a pressure of 80 pounds in 
the first receiver, the injector will work discharging and induc- 
ing free air into a second receiver in which is maintained a 
pressure of 60 pounds. 



THE SAND BLAST. 

The energy contained in a single flying grain of sand is 
small, even when travelling at a very considerable velocity, 
but it is the exceedingly small area upon which this is ex- 
pended that makes any cutting by it possible. As an illustra- 
tion of the above points, take, for instance, the case of a sand 
blast using sand of an average of -^ inch in diameter and pro- 
pelled by air of 50 pounds to the square inch, cutting granite. 
Such a blast, under these circumstances, will cut granite rap- 
idly. Why? Determining the above factors, first, such sand 



PNEUMATIC WORK. 63 I 

grains will weigh on an average about 0.005 grain and will be 
moving at the point of impact with the stone about 400 feet per 
second, and will therefore contain about 0.00176 foot-pound 
energy. Now, this is certainly a very small amount, but next 
take the area upon which it is expended. 

The area of first impact can only be estimated from the fol- 
lowing considerations: If a piece of smooth, hard substance is 
scratched with the edge of crystal, as, for instance, in ruling 
diffraction gratings and that class of work, lines are readily 
ruled at the rate of .00002 to the inch, and when examined 
under the microscope the lines are seen to be narrow in com- 
parison to the space separating them, being themselves proba- 
bly not more than 50 ^ 00 inch broad, and it is upon a rectangle 
of the length of side equal to the breadth of one of these lines 
that the first impact occurs. This is .000000004 square inch. 
And the above-determined 0.00176 foot pound of energy dis- 
tributed upon this area is at the rate of 440,000 foot pounds 
per square inch. Now, the strongest granite can stand only a 
quiet crushing strain of some 1,200 tons per square foot, or at 
the rate of some 16,600 pounds to the square inch. The con- 
test between the stress developed at the point of impact and the 
resistance of this object struck is in this case decided over- 
whelmingly in favor of the stress developed. The result is that 
the granite under the point of the first impact is crushed and 
crumbled to dust, letting the grain of sand progress until in its- 
advance it has expended its energy and increased the area of con- 
tact, when the pressure there falls below the crushing strength 
of the granite, and then the action of that grain is over and it 
rebounds from the stone. The striking edge or point of the 
grain of sand is also crushed, and contributes to increasing 
the area of contact between it and the granite. The effect of the 
above sand blast, when striking a piece of wrought iron in place 
of the granite, will be that the iron, instead of being pulverized 
like the granite, is only indented. The result is that no metal 
is removed, but a small indentation produced. Other grains 



632 COMPRESSED AIR AND ITS APPLICATIONS. 

striking in the immediate vicinity of this indentation simply 
shove the metal back into it again and obliterate the effect of 
the first grain. Thus no effect is produced, but the surface is 
simply roughened by the indentations of the sand grains. This 
is the normal effect of the blast upon all metals. If they are 
exposed for a long time to the action of the sand, as in a sand- 
blast machine, metals wear away, because the surface metal is 
exhausted by the constant bending so that it at last breaks. If 
the blast is directed upon a piece of soft rubber the same action 
as in the case of the metal takes place, but in this case the elas- 
ticity of the rubber is such as to enable it to resume its original 
shape after the force of the impact has been expended in de- 
forming it, and there is no residual effect whatever upon the 
rubber, the grain of sand rebounding with almost its original 
velocity. These three actions and the combinations of them 
explain all the different effects of the sand blast, in cutting and 
refusing to cut various substances. 

In surface obscuring or ornamenting, such as in glass work, 
for which the sand blast has been more used than for all other 
purposes combined, the problem is entirely different. The 
effect wanted is to break the continuity of the surface struck, 
and this once obtained any further force in the blow of the 
sand is wasted, and an exceedingly great number of light blows 
is what is desired. Therefore a very fine sand is used and a 
large quantity thrown in proportion to the propelling jet, which 
gives a moderate velocity. So important is the adaptation of 
the size of sand to the work that if two exactly similar machines 
are taken, one using fine and the other coarse sand, and both 
using the same pressure of air to drive the sand and the same 
size jet, the machine using fine sand will obscure three times 
the work that the machine using coarse sand will do. But in 
cutting or perforating glass or stone the machine using coarse 
sand will do three times the work of the machine using fine 
sand. In one case the blows are too few to break up much sur- 
face, and in the other case they are too light to do much cut- 



PNEUMATIC WORK. 



633 



ting. Thus, by use of sand unsuited to the work, the efficiency 
of a good machine can be reduced over 60 per cent. 

THE SAND BLAST AND ITS WORK. 

The economy of the sand blast to lighten the labor of clean- 
ing castings in the foundry is a most important use of air apart 
from the melting blast. With it, the air hoist, the moulding 
machine, and the air lift, and we may add the air rammer, have 
brought the work of the found^ to a high degree of perfection 
and economy in their labor-saving aspects. On an average it 




Fig. 449.— ward & nash apparatus. 

now takes but one-third of the time to clean a casting or the 
day's run, as was formerly the case by hand. 

Neither files nor brushes can get around recesses, fins, and 
risers as the blast does, and when so cleaned the air-chipping 
hammer has a clean path for work. 

In Fig. 449 is illustrated the Ward & Nash sand-blast ap- 
paratus at work. The sand is fed to the air pipe as shown in 
Fig. 450, and carried through a short rubber hose and ejected 
through a nozzle at great velocity, estimated at from 350 to 
500 feet per second. At this great velocity the sand has an 
intense cutting power. 

For small castings suitable for the tumbling barrel, the sand 
blast facilitates and preserves the sharp corners of castings to a 



634 



COMPRESSED AIR AND ITS APPLICATIONS. 



marvellous extent. The barrel used for this work is open at 
both ends and revolves on rollers ; the sand blast enters at one 
or both ends of the barrel, while it slowly rolls the castings 
over. In the detail of the sand tank (Fig. 450) the compressed 
air enters the lower compartment at B, and issuing through the 
cross pipe D receives its charge of sand graduated by the slide 
valve F, which is regulated by the lever E. C C is the conical 
partition that holds the sand in the upper chamber. A is the 
inlet valve held in place by a spring. The upper section is the 
hopper into which the sand is dumped, when by pushing down 
the spring with the valve F closed the 
sand drops into the feed chamber. 

For the foundry sand blast an air 
pressure of 25 pounds per square inch 
seems to meet the requirement ; but 
where hoists, hammer-chipping tools, and 
rammers are used that require higher 
pressure, the sand-blast pressure can be 
readily throttled to the requirement of 
its best work. 

For the different uses of the sand 
blast the abrasive substances may be clean 
silicious sand as builders' sand, sea-beach 
sand, emery from fine to coarse, chilled iron sand, and steel 
shot; sand from its plenteousness and general suitability is 
mostly employed. The heavier material, as emery and chilled 
iron, require higher air pressure to give the best cutting 
velocity. 

The action of the sand blast is not cutting, not grinding, 
not abrading in any of the usual meaning of these terms. It 
is a true pulverization by the successive impact of the grains of 
flying sand. The sand acts much in the same manner, but on 
an infinitely reduced scale, as artillery projectiles in breaching 
a masonry wall, each independently of all the rest. In this 
action it differs from anything that has preceded it, and it still 



1 


A 

\c 0/ 


2 


u 


1 1 r 















Fig. 450.— sand-blast tank. 



PNEUMATIC WORK. 635 

stands alone. It is this difference between its action and all 
other processes that has caused the general misunderstanding' 
about it above referred to. As all know, the process consists 
simply in driving a stream of rapidly moving sand against the 
object to be operated upon. How the sand is given velocity, or 
how the work is presented to the blast, are matters of indiffer- 
ence when examining the theory of the process. As the total 
action of the blast is but the summation of the action of the 
individual grains, the action of the individual grain is to be 
considered. If the single grain of the flying sand has no effect 
when it strikes the work, then no other grains will have any, 
and the sand blast will be without effect, no matter how long 
continued. If, however, the single grain of sand has any effect 
upon the object struck, then the blast will wear it away, often 
at an extraordinary speed, as the number of grains propelled 
against it is very large, often as many as 5,000,000 per minute. 

Grains of sand have numerous angles, and the action of 
these grains — as also that of the other abrasives mentioned — 
upon the surfaces of glass, stone, or metal, is due to the cir- 
cumstance that every individual grain in the incessant infinite 
number in the stream urged violently forward has all its energy 
instantly arrested, transferred, and concentrated upon its point 
of impact, where it produces a minute pit or depression ; and, 
as every grain in the shower acts alike, the abrasion resulting 
from the whole is perfectly uniform in depth and texture or 
roughness. 

The action, moreover, is extremely rapid; a momentary ap- 
plication depolishes glass over any space that can be covered by 
one stroke of the sand shower, instantly changing the previ- 
ously bright surface to obscured or that known as ground glass. 
A little longer exposure cuts more deeply, and, with further 
time, apertures are readily pierced through sheet and plate 
glass. 

Stone, marble, slate, and granite are just as amenable to its 
action. Iron, steel, and other metals have their surfaces easily 



636 



COMPRESSED AIR AND ITS APPLICATIONS. 



reduced, and smoothly or coarsely granulated, according to the 
force and abrasive power used ; but all these materials, being 
less brittle than glass, take a rather longer time. Speaking 
generally, it appears that the harder or more dense the material 
acted upon, and the higher the velocity given to the sand, the 

more rapid the cutting action ; 

and the finer the abrasion, and the 
lower the pressure of the air, the 
finer the granulation produced. 
It is also remarkable, that it is by 
no means necessary that the abra- 
sive be harder than the material 
to which it is applied ; thus, hard- 
ened steel and corundum are 
readily pierced with sand. 

This granulating, scaling, in- 
cising, and piercing, however, is 
but one-half of the process, for, if 
the work be partly covered and 
protected by some slightly yield- 
ing but tough substance, adhesive or in the form of a metal 
template lying closely upon it, this interposed substance in- 
stantly diffuses the shock of the particles and neutralizes their 
abrasive power. The action of the sand blast is thus confined 
to the unprotected portions of the surface, and these overlays 
and templates are used on glass, stone, slate, pottery, and metal 
for surface ornamentation, for deeper intaglio and perforations. 
An early exhaust-air sand-blast machine is illustrated in 
Fig. 451. It had a closed iron drum D, about 20 inches diam- 
eter, with an open central pipe i>, and below the latter a verti- 
cally adjustable plate P. The head of the drum had an aper- 
ture about 4 inches in diameter, closed by the work, overlay 
downward, lying upon it, the exhaust being at E. The sand 
from a closed box falls down the pipe A to the bottom of the 
drum, on to the plate P ; thence impelled or sucked up the blast 




FIG. 451.— EXHAUST SAND blast. 



PNEUMATIC WORK. 



637 



pipe B by the external air rushing in above the plate P, it strikes 
the work, which is moved about by the operator, who looks 
through the glass to watch the progress of its frosting. Most 
of the sand falls back to the bottom of the drum; some, with 
the dust pulverized from the glass, is carried along the exhaust to 
a sand-catch box. The air pressure need not exceed one pound 
to the square inch, the frosting is almost instantaneous, and the 
hand may be held in the blast without inconvenience. Several 
machines are connected to one exhaust running round the 
workshop ; they are used for small work, but are applicable to 
sheets as large as can be conveniently moved about by two 
men. 

A small vacuum or exhaust sand blast is shown in Fig. 452. 
It has a bellows formed of a heavy plunger A connected to the 
sides of the drum by an india-rubber apron or diaphragm and 
by a cord to a lever, by which it is 
operated like a suction bellows, the 
valve E acting as the discharge 
valve. The base of the blast pipe, 
of \\ inches bore, is surrounded by 
a cup, S, pierced with holes below, 
and beneath there is a vertically 
adjustable plate or disc. The sand 
placed in 5 falls on the plate, and 
is carried up by the inrush of air 
between that and the lower end of 
the blast pipe to strike the work; 
it then falls and collects in the base 
of the drum. The plunger is raised 

for every impression, the lever being worked by an assistant, 
sometimes by standing his weight upon it ; in smaller machines, 
it is placed close to the blast, and worked by the left hand, and 
the objects to be frosted are changed by the right. 

A form of exhaust-air sand-blast machine is shown in Fig. 
453, in which the drum has a large exhaust chamber, E, open 




-EXHAUST SAND BLAST. 



638 



COMPRESSED AIR AND ITS APPLICATIONS. 




-VACUUM SAND BLAST." 



below and worked from above; D also carries the sand, which, 
falls through a pipe, regulated by a valve, into the open end of 

the tube, T, i-|- inches diameter, 
which, bent upward, terminates 
within the open bell mouth of the 
lower end of the blast pipe B, 2 
inches diameter, outside the drum. 
The upper end of B is contained 
within a box, called the working 
chamber, provided with an aperture 
above, upon which the glass is 
placed. The sand carried up T, by 
the current induced by the exhaust, 
as it issues is caught by the stronger 
current of external air entering all 
around the open bell mouth of B, 
and thus accelerated travels upward and strikes the work. The 
exhaust then carries the spent air and sand from the working 
chamber, W, to the annular space 
D\ here both circulate spirally 
around, and to the bottom of E, 
the heavier particles of sand strik- 
ing the sides of D by centrifugal 
force, and falling to the bottom, the 
lighter particles and the dust pulver- 
ized from the glass, travelling with 
the air up within E, and along the 
exhaust pipe E. Virtually free 
from the escape of sand, the ma- 
chine almost entirely sifts the dust 
from the sand, which latter is used 
again and again. Large sheets of 
glazing glass, covered with their overlay designs, are thus 
frosted to the form of the pattern. 

In Fig. 454 are represented two forms of pressure air sand- 



^j» 




FIG. 454.— pressure sand blast. 



PNEUMATIC WORK. 



639 



blast nozzles. These nozzles have been made as round and 
flat blast pipes, which postpone the mingling of the air with the 
sand until both have issued from the nozzle. The straight pipe 
in the upper portion of Fig. 454 represents the pipe through 
which the sand arrives by gravity or otherwise ; this is sur- 
rounded by the enlarged hollow head of the air pipe, A, the 
one adjustable lengthwise within the other to determine the 
— extent of the annular space between their open tapering ends ; 
the air rushing up A issues through this space, and, converging, 
catches up and carries the sand for- 
ward, the two only mingling at the 
point shown by the vertical dotted 
line, well beyond the end of the 
nozzle. 

The lower figure represents this 
principle with a sand box and valve 
attached which can be operated by 
the thumb as the hand grasps the 
handle. 

A form of sand-blast cylinder 
which allows of recharging without 
interrupting the operation of the 
sand blast is illustrated in Fig. 

455- 

The external cylinder, D, is fig. 4S5 .-air-lock sand-blast 

TANK. 

divided into three compartments, 

two air-tight and the topmost a hopper open above. The 
sand, shovelled through a sieve in this last, falls through 
valves into compartment 2, thence through similar valves into 
the open-mouthed sand box, 5, fixed in compartment 3, and 
from this through a funnel-mouthed pipe into the open end of 
the delivery pipe, B. The compressed air enters at A, fills 
compartment 3, inclusive of the space above the sand in the 
box S, and dries the sand as it falls from the latter along B to 
the blast pipe, a piece of plain chilled iron or steel tube from 




64O COMPRESSED AIR AND ITS APPLICATIONS. 

T 5 ¥ to |-itLch bore, which is held in the hand at the further end 
of a length of flexible hose attached to the end of B. The sand 
in 5 being in equilibrium as regards pressure of air, falls freely 
by gravity ; its volume is regulated by a screw sliding valve, the 
head of which is outside the drum. Compartment 2 is also 
filled with compressed air from a branch of the pipe A, but this 
is allowed to escape by the relief valve in order to open the 
valve in the hopper every time fresh sand is added, so that the 
issue of the sand blast is continuous and uninterrupted. The 
recent improvements and inventions of Mr. Matthewson, man- 
ager of the Tilghman Sand Blast Company, Sheffield, England, 
have given a new impetus to the use of the sand blast for a 
great variety of purposes. In these machines the best points 
have been retained, and there has been secured also the full 
efficiency of the blast, due to the pressure at which it is used, 
unreduced by the admixture of any dead air carrying the sand 
with it, at just the place where the maximum velocity is de- 
sired. This machine uses air at all pressures, but those about 
ten pounds to the square inch are found to be the most satisfac- 
tory. By immersing the whole sand supply in an atmosphere 
of air at the above pressure, contained in a tight reservoir, the 
advantages of a pure gravity feed are obtained, uncomplicated 
by any questions of difference in pressure inside of the jet tubes 
and without. Then, by the use of a flexible tube of considera- 
ble diameter, the sand and air, in a mixed current, are carried 
to a point where they are to be used. Here the flexible tube is 
connected with a hard chilled iron cone, terminating in a tube 
of small diameter. In traversing this latter portion of its 
course the mixed current of sand and air increases its velocity 
inversely as the square of the diameter of the tube, and is 
finally discharged from the end of the blast nozzle at the full 
velocity due to the pressure behind it. An air-lock arrange- 
ment for transferring new supplies of sand into the sand re- 
servoir, while still under pressure, and valves for operating 
and graduating the air and sand supply, with a suitable com- 



PNEUMATIC WORK. 64I 

pressor for furnishing the supply of compressed air, complete 
the arrangement. 

In metal it is used for the removal of the hard scale, so de- 
structive to cutting tools, from castings and forgings. Among 
the applications are the removal of the scale from sheet iron 
and steel prior to enamelling, galvanizing, nickelling, tinning, 
etc. ; the cleaning of tubes and brazed joints, largely used in 
bicycle work ; sharpening the teeth of files ; for granulating or 
frosting electroplate, gilding metal, gold- and silversmiths' work, 
and jewelry ; the reduction to clean metal surfaces of larger 
works, ranging from steel forgings of safes to armor plates; on 
stone, slate, and granite, for incised carvings and inscriptions 
in intaglio or relief; for cleaning off the grime from stone, 
granite, and brick buildings, and, in contrast to this last, for the 
most delicate drawing for lithography. 

Among other purposes it is employed for removing fur and 
deposits in tubes and tanks ; for cleaning off accumulations of 
paint and dirt within iron ships ; for roughening the surfaces 
of metal rollers; for decorating coat and other buttons; for 
granulating glass to give it a key for ornamental painting by 
hand ; for piercing the apertures in glass ventilators ; for mark- 
ing cakes of glue and cement ; for marking pottery and in the 
manufacture of ornamental tiles ; for smooth-facing bricks to 
receive white glass or enamel; for refacing grindstones, emery, 
and corundum wheels ; for granulating celluloid films for pho- 
tography, and on wood to bring out the grain in relief, and 
latterly for blocks for printing. 

For stone, marble, slate, and granite, the abrasives are sand, 
emery, and chilled iron sand, delivered at from 10 to 15 pounds 
pressure, usually from the compressed-air apparatus already 
described. The overlays are similar to those for glass; if for 
original designs, they are cut of thick porous paper saturated with 
the glue and dextrine, by which also they attach to the plain or 
polished stone; for work often repeated they are frequently 
iron stencil plates. The quick, yet gentle action of the process 
41 



642 COMPRESSED AIR AND ITS APPLICATIONS. 

annuls all risk of "plucking" or splaying the stone; but in 
some materials and marbles and in granite, which may be con- 
sidered conglomerates, the harder are rather less cut away than 
the softer constituents ; the sparkling granulation then pro- 
duced is itself decorative, but, if required, it may subsequently 
be smoothed and polished. 

Granulating designs with overlays and frosting on moderate- 
sized works in metal are generally conducted within a closed 
drum or box glazed on one or more sides to watch progress, and 
with holes in the sides of the box with elastic sleeves for the 
hands to hold the work in the vertical sand blast. 

A beautiful translucent variety, known as chip or crystalline 
glazing glass, covered with gray filaments and fern and feath- 
ery markings on an ice-like ground — is also remarkable for the 
peculiarities of its manufacture. The surface, first uniformly 
frosted with the sand blast, is then covered with a coat of 
strong glue, and when this has set, the sheets are placed in 
horizontal racks in a room heated to 160 . In the course of ten 
or twelve hours, the hardening glue audibly cracks and springs 
off in patches, bringing away thin flakes of the glass with it. 
The fern-like markings are irregular portions of the original 
sand-blasted surface which remain on these flat conchoidal 
fractures. 

This simple process was discovered by an accident, and 
put to use by Mr. Corsan in England. Beyond the curious fact 
that glue, under such conditions, will tear flakes from glass, 
the explanation appears to be that the hardening glue gradu- 
ally blisters, and these blisters, as they detach, tear off more of 
the glass by their margins than toward their central portions, 
which latter leave the fern-like markings. By the employment 
of the ordinary overlays prior to frosting and gluing, the crys- 
talline effect is sharply localized and confined to any portion of 
a design. 

Lamp globes and spherical objects are plain or pattern- 
frosted all over their superficies in an ingenious manner. The 



PNEUMATIC WORK. 



643 



drum of the machine — about as high as its diameter — has a 
hinged cover, and moves round on a central vertical pivot. 
Diametrically within the drum is a spindle, or rather the two 
ends of a spindle, its central portion removed and replaced by 
corresponding rods, with spring means of holding, which carry 
the glass globes. The globe when in its place is exactly in the 
centre of the drum, and the tube of the sand blast, presented 
horizontally, points to the centre 
of the globe. During the frosting 
the spindle is continuously turned, 
and the drum itself moved round 
on its pivot through about a half- 
circle, both automatically ; the cen- 
tral line of the spreading sand 
shower — its most active part — thus 
always points to the axis of the 
globe, which secures absolute uni- 
formity in the texture of the frost- 
ing. Dry sand and air, at about one 
pound pressure, are used for ordi- 
nary work, and very fine sand, with 
steam at about 20 pounds pressure, 

for the best class of this work. The globes are replaced with 
expedition, and from 60 to 100 may be completed in an hour. 

In ordinary lithography the design is drawn on the pure, 
smooth, polished stone in a greasy chalk or ink, and, although 
almost inappreciably, really stands just in relief; when printed 
from, the stone is kept constantly wet with water, which repels 
the ink — applied with a roller — from all parts of its surface, ex- 
cept the greasy lines of the drawing ; upon these the water can- 
not stay, and they alone receive the ink and print. 

In sand-blast lithography this is partly reversed. The 
whole surface of the stone is first impregnated with grease, so 
that, if then inked, it would print a uniform black ; and this 
surface is then eaten away to a trifling depth with the sand 




Fig. 456.— drum sand blast. 



644 COMPRESSED AIR AND ITS APPLICATIONS. 

blast, to entirely remove the grease from all portions that are 
not to print, that is, which are to give white; to granulate, or 
more or less destroy it upon those to give different tones of 
shading ; and to leave it intact upon those that are to print 
black. All that remains of the original greased surface, there- 
fore, alone prints; the stones being wetted, as usual, prior to 
inking for every impression. 

Sand-blast engraving has been tried for steel-plate printing, 
and, although still in the experimental stage, it gives good 
promise of a future. The granulation from the fine emery 
powder gives the character of a mezzotint, but unlike an ordi- 
nary plate, upon which the rocking is generally uniform, so 

3 that it would print a solid 
block, and is then reduced 
in tones by scraping and bur- 
nishing to produce the draw- 
ing, the granulation of the 
sand blast may be localized 

Fig. 457.— the file sand blast. 

and arrested on any portion 
at any depth of tint ; thus reducing the subsequent scraping to 
a minimum. In printing, the plates are treated just in the or- 
dinary manner; the whole surface is inked, wiped clean of the 
ink, and finally polished with whiting on the palm of the hand. 
Worn-down files are resharpened in the sand blast by being 
slowly drawn several times from tang to point between two 
converging streams of fine sand — sand worn so fine in grinding 
plate glass as to have become valueless for that purpose, and a 
waste product, is preferred — projected by compressed air at about 
60 pounds pressure, which pass on from the file into a receptacle 
for reuse. The effect is rapid, and on both sides of a flat or on 
all four sides of a square file simultaneously, a fourteen-inch 
rough or bastard file being resharpened in two or three minutes ; 
on second cut and smooth files the blast acts stiirmore quickly, 
blasting away the curves until they again meet the upright 
sides of the teeth, and at but little less angle than before. 




PNEUMATIC WORK. 



645 



The file throughout the process is drawn across a piece of gun 
metal fixed between the sand blasts, and the equal hang of the 
teeth to this " feeling piece " tells the operator the resharpen- 
ing is uniform from end to end. 

The thorough work of the sand blast has been recently dem- 
onstrated in the cleaning of old paint and dirt from structural 
steel work for preparing it for repainting, the structure being 
the viaduct at One Hundred and Fifty-fifth Street, New York 




Fig. 458.— sharpening files. 



City, which had been painted many times to prevent injury to 
the steel trestle-work by the smoke and gases of the Elevated 
Railway locomotives. Rusting had taken place under the many 
coatings of paint, and blistering and peeling had given the 
work an unsightly appearance with indication of damage to the 
structure. For this work compressed air was conveyed about 
300 feet from a compressor to a receiver, and to the sand-mixing 
apparatus on a temporary flooring in the trusses of the viaduct. 



646 COMPRESSED AIR AND ITS APPLICATIONS. 

A hose connects the sand-mixer and nozzle, which was held 
close to the surface to be cleaned. A section of the trusses was 
made perfectly clean in the early part of the day, and at once 
painted by the air-blast process, thus giving the paint a perfect 
contact with the metal and by this means obviating the formation 
of rust from loose scale. 

For cleaning the walls and trimmings of buildings the sand 
blast has proved a perfect success. For removing the smoke 
and fire stains on the walls of buildings that have been burned 
and are found safe for rebuilding, the sand blast has been a 
saving clause in the expense of rebuilding, as was tested in 
cleaning the walls of Pardee Hall, Lafayette College, at Easton, 
Pa. The stone facing and trimmings of the New York Central 
& Hudson River Railway station in New York City have under- 
gone a most satisfactory renewal by the sand-blast process. 

The air blast finds one of its useful effects in sanding paint 
on car roofs and buildings wherever sanded paint is needed for 
special protection. The sand thus thrown with great force im- 
beds itself in the paint, and the air blast without the sand 
blows off the excess. 

The air blast is also used for feeding coal dust and fine 
culm to boiler and other furnaces, and in the petroleum burner 
with its steam combination it contributes a most important 
condition in the combustion of liquid fuel. 

Fig. 459 illustrates a petroleum burner, for a furnace, for a 
boiler, or other requirements. A, entrance of oil to central 
nozzle, which is regulated by a needle valve with screw spindle 
and wheel, C ; B, entrance of compressed air to the annular 
nozzle, the force of which draws the oil and atomizes it for 
quick combustion. 

The air blast is also used for elevating, drying, and aerating 
grain, for elevating coal culm, and discharging ashes. 

Compressed air is also used for discharging the oil from 
tank cars to a higher level by sealing the manhole and forcing 
air above the oil. 




PNEUMATIC WORK. 647 

The discharge of sand, soft material, and water from the 
foundation caissons of bridge piers by the direct action of com- 
pressed air has become a most important adjunct in caisson 
sinking, and was used in sinking the caissons of the Brooklyn 
and New York bridges to great advantage. A pipe, usually 
about four inches, is inserted in the 
roof of the caisson, extending up 
through the loading masonry and 
overboard to a scow. The lower 
end is extended down to a sump, 
with a quick-opening gate. The 
sump is used for a drain basin, into 

, . , . .. ., . Fig. 459.— petroleum burner. 

which sand, clay, and mud are 

thrown and ejected with great velocity by the air pressure in 
the caisson; the air lock being used for the passage of the 
men, tools, and material required for the sub-masonry. 

THE AIR BLAST IN PAINTING. 

The air blast for painting is comparatively a late innovation 
in the old and staid art of wielding the paint-brush by hand; 
but the times are progressive, and the use of compressed air in 
the arts keeps pace with its extending use in mechanics. Like 
all other progressive movements leading to new ways and 
means, this is also a labor-saving operation and is becoming an 
important and economical helper in the work of painting. For 
structural work, bridges, and the painting of railway cars, it 
is gaining a fast foothold for good and economical service. Tt 
is not only used for oil painting, but has proved a most efficient 
method of whitewashing and kalsomining walls and fences. 
Further, the finer points of the artist's conceptions have taken 
the air blast in hand for pictorial illustration. The atomizing 
of colored fluids in a spray from sharp lines to faint shadows is 
the outcome of the air-blast process, which has been applied to 
the production of picture work. 



648 



COMPRESSED AIR AND ITS APPLICATIONS. 




Fig. 460.— hand air paint- 
pot. 



The simple hand compressed-air paint-pot is shown in Fig. 
460. The thumb key is for regulating the air blast, and the 
valve wheel at the left side regulates the flow of the paint. 
The paint pipe starts from the bottom of the can and joins the 
air pipe and spray nozzle as shown in 
the cut. 

Fig. 461 represents a paint-spray 
nozzle as usually constructed. The inner 
or air nozzle, usually i-inch opening, is 
made on the best lines for high air veloc- 
ity and is fixed central to the larger open- 
ing in the inverted conical nosepiece, 
which is flattened to a thin opening, -fa inch, to project the paint 
spray in a thin sheet. The paint is drawn in at the side inlet 
of the tee piece, and both air pressure and paint supply are 
regulated by valves, both pipes being under the same pressure 
from the paint tank of from 50 to 80 pounds per square inch. 

In Fig. 462 is detailed the Mason painting machine, which 
consists of a steel paint tank strong enough for a working press- 
ure of 100 pounds per square inch; a small hand air pump 
"mounted upon the top of the tank, with suction and pressure 
pipes connected to the top 
of the tank in which are the 
three-way cocks A and B. 
To the tank connection at F 
is a pressure gauge and the 
air pipe and cock at C. E 

is the paint discharge pipe. The tank is charged from the mix- 
ing barrel by the siphon and cock D. 

The operation, then, is as follows: to charge the tank,. the 
cock D is closed, the three-way cock A is turned to communi- 
cate the suction of the pump with the tank. The three-way 
cock B is turned to discharge the air at its side outlet with clos- 
ure on the tank, the cock C being closed. The pump is then 
operated to exhaust the air from the tank, producing a degree 




Fig. 46T.- paint spray nozzle. 



PNEUMATIC WORK. 



649 



of vacuum measured by the gauge, which is both a vacuum and 
pressure gauge. The cock D is then opened, and the paint 
mixture is drawn into the tank in the desired quantity, or for 
continuous work about two-thirds full. Cock D is then closed: 
cock A is turned to shut off the tank connection and to draw air 
from the side inlet ; cock B turned to connect with tank and 
shut off side exit. The pump can then be operated to charge 
the tank with the desired air press- 
ure. For operating the spray, the 
paint hose is connected to the cock 
E at the bottom of the tank and the 
air pipe to the cock C at the top of 
the tank with the valves on the 
spray nozzle closed. The cocks C 
and E are then opened, which gives 
a balanced pressure in both pipes. 
When ready, open the air valve on 
the spray nozzle, and then the paint 
valve to meet the requirement of 
the spray. The ejector power in 
the nozzle draws the paint by over- 
coming the static pressure. 

By varying the opening of the 
valves of the spray nozzle any den- 
sity of the spray may be had from 
a thin cloud to a solid paint stream. 

The air pump must be kept in operation to keep up the press- 
ure according to the relative proportion of air and paint ejected. 
The nozzle should be moved slowly broadside over the work; 
a jerky motion scatters the paint. The same machine works 
equally well with whitewash or kalsomine. 

In Fig. 463 we illustrate the Mason painting machine as 
operated by an electric motor belted and geared to a triplex 
air pump. By this arrangement the motor and pump can be 
placed in a convenient location for electrical connection and 




($IDE £LiVaTIO[^ 

Fig. 462.— mason painting machine. 



650 



COMPRESSED AIR AND ITS APPLICATIONS. 





PNEUMATIC WORK. 



6 5 I 



the hose extended to the tank, which should be in proximity to 
the work. 

In Fig. 464 we illustrate the magnite spray painting ma- 
chine made by J. A. and W. Bird & Co., Boston, Mass. It is 




Fig. 465.— pneumatic paint machine. 

Used as a hand painting-machine for car and structural iron painting. A record of four- 
teen minutes has been made with one of these machines in painting an ordinary box car. 
They are made by the Chicago Pneumatic Tool Company. 



a portable machine, having all its parts mounted on a platform 
with casters. A two-cylinder air pump with single-acting trunk 
pistons operated by a hand lever, and with an air receiver' 
and pressure gauge, constitute it a very simple and complete 
apparatus for spray painting with oil paints, kalsomine, and 




Fig. 466.— car-deck painting. 



6 5 2 



COMPRESSED AIR AND ITS APPLICATIONS. 




Fig. 467. — car-side painti 



other water paints, and for spraying antiseptics in hospitals, 
cellars, and on brewery walls. In fact, there seems to be no 
end to the uses that an atomizing machine can be utilized 

for. Paint machines are 
readily cleaned by pump- 
ing naphtha through 
them, discharging back 
into the tank. 

The spray painting of 
railway cars has now be- 
c o m e an accomplished 
fact, and is in practice on 
a number of railways. 
We call attention to 
the fact that a perfectly atomized sprayed-on paint will almost 
instantaneously reach, cover up, and consequently protect a 
car's most complicated structural parts. It penetrates the rough 
beaded work — the open joints through shrinkage of sheathing 
■ — the crevices and other disfigurements usually met with when 
painting the new and repainting ..,. ,_ 

the old railway freight-car equip- 
ment. 

There is evidence of the close 
observation made, from time to 
time, of sprayed freight cars and 
other large surface work done by 
the P. & L. E. R. R. Company, in 
the beginning, convincing us that 
the results from a standpoint of 
durability will not suffer on the score of fact that the paint 
was not applied with a brush. 







Fig. 468.— truck painting. 



PNEUMATIC WORK. 



COMPRESSED AIR FOR DUSTING AND CLEANING. 




Fig. 469.— curved nozzle. 



A novelty among- the several hundred applications of com- 
pressed air for useful work and for time-saving in labor, is the 
air blast. It is only in recent years that the power of the air 
blast has been used for cleaning the dust 
from carpets, walls, ceilings, furniture, 
car seats, and, in fact, every place where 
dust can find a hiding-place. Not only 
this, but where disinfectants are needed 
the air blast is the most convenient vehi- 
cle for their distribution for best effect. 
In this manner dwellings and public build- 
ings may be quickly and cheaply renovated even to the dra- 
peries and bedding. Air can now be bottled at 3,000 pounds 
pressure per square inch, and thus made portable to be con- 
veyed for use in any locality. Where an electric current can 
be utilized, an electric motor becomes a part of the house-clean- 
ing kit for compressing the air. A gasoline-motor compressor 
on a light wagon becomes a complete portable outfit for house- 
cleaning, only requiring the ex- 
tension of its air hose to the 
rooms or localities to be cleaned. 
In Fig. 469 is illustrated the 
form of an air-spray nozzle for 
dusting with compressed air. 
This is a broad, thin nozzle from 
which a blast of compressed 
air penetrates fabrics, cleaning 
them of dust; a good cleaner 

of plain and carved woodwork. The open slit should vary in 
width from one-thirty-second to one-sixteenth of an inch, and 
in breadth from one to six or more inches, according to the kind 
of work it is to do. 

The straight-edge nozzle (Fig. 470) is the most suitable for 




Fig. 470.— straight nozzle. 



654 COMPRESSED AIR AND ITS APPLICATIONS. 

flat work such as car-seat cushions and carpets that are dusted 
out-of-doors. 

In Fig. 471 is illustrated a suction nozzle in which the com- 
pressed air is ejected against the point of the inverted cone, 




-SUCTION NOZZLE. 



which induces a strong current of air upward and from under 
the bottom of the inverted funnel, drawing the dust from the 
fabric and projecting it through a hose out of the windows; 
much used in car-seat cleaning. 

For carpet-cleaning in dwellings where it is not convenient 
to use a hose for ejecting the dust through the windows, a filter 
hood or dust collector is used, which allows the air to pass 
through, retaining the dust on the inside. The filter hood is to 
be taken outside and cleaned when 
it becomes charged with dust. >^\ 

The carpet-cleaner as illustrated ..;-, \ JRk 

is a box-shaped arrangement into 
which is injected a blast of air twelve 
inches long and one-hundredth of an 
inch wide. This blast strikes the 
carpet at an angle of 45 ° under a 
pressure of 75 pounds per square inch, 

Fig. 472.— filter hood. 

removing all the dust from the carpet 

and depositing it in the receptacle. The cleaner is pushed over 
the carpet the same as an ordinary sweeper, and, besides re- 
moving all dust, the effect of the compressed air is to restore 
the carpet to its original color. 

The cleaning of dwelling-houses and hospitals and the dis- 






PNEUMATIC WORK. 



655 



infection of walls, carpets, and furniture are coming largely into 
practice with the best results, and are now being conducted by 
the General Compressed-Air House-Cleaning Company, St. 
Louis, Mo. 

In Figs. 472 and 474 is shown the disinfecting attachment 
on the pipe handle of the air-blast machine. A glass reservoir, 
somewhat like an automatic oil cup, is attached to the pipe 




Fig. 473.— carpet cleaning with the filter hood. 

handle, with an air connection both above and below the fluid 
with a cock to regulate the flow of the disinfectant. 

For spraying walls and ceilings the reservoir connection is 
inverted and a spray nozzle takes the place of the box. 

In Figs. 475 and 476 is illustrated a machine for cleaning 
and removing dust from carpets and other similar fabrics by 
the air-blast process ; it is in use in carpet-cleaning establish- 
ments. 

Hitherto, when machinery has been used for this purpose, 
the system employed has merely been an amplification%£ the 



656 



COMPRESSED AIR AND ITS APPLICATIONS. 



crude method of hand-beating, sticks, chains, straps, or ropes 
being used. Carpets submitted to this beating or "hammering" 
process are frequently torn and otherwise damaged ; holes are 
enlarged, and worn, tender places are made into holes. In the. 
air process illustrated all chance of damage is eliminated, as 

no form of beating 
whatever is resorted to, 
the cleansing being ef- 
fected solely by the 
use of minute jets of 
compressed air driven 
at a pressure of 45 
to 50 pounds per square 
inch entirely through 
the fabric. These 
carry along with them 
every particle of dust 
from the carpet with- 
out any damage what- 
ever. The illustration 
(Fig. 475) represents an 
elevation of the pneu- 
matic carpet-cleaning 
machine, and Fig. 476 
an elevation at the driv- 
ing end of the machine. 
From these it will be 
seen that nearly the whole of the machine is enclosed in a 
hexagonal casing provided at each side with swing doors for 
the insertion and withdrawal of the carpets. Compressed air 
is conveyed from the main pipe by means of the two flexible 
branch pipes to the longitudinal feeder pipe running the entire 
length of the machine. This pipe is fitted at intervals of two 
inches with a number of nozzles, each having small holes at its 
nose, through which the compressed air escapes in minute jets 




Fig. 474.— disinfecting attachments. 



PNEUMATIC WORK. 657 

at great velocity, onto and through the carpet. This is carried 
slowly under the jets by the central wire roller, to which a 




Fig. 475.— carpet-cleaning machine. 

rotary motion is given by the bevel wheels and driving pulleys 
shown. After the carpet has once been passed through the 
machine by the roller, if found desirable — as in the case of very 
thick carpets — it can be passed through a second time by revers- 
ing the action of the revolving roller. The feeder pipe carry- 
ing the nozzles rides at each end on trunnions, carried by an 
upright lever and shaft, to which an oscillating motion sidewise 
is given from the driving shaft by an eccentric and rod ; the 



I \m 



object of this oscillation is to 
thoroughly distribute the air 
currents over the entire surface 
of the carpets passing under it. 
This pipe is further divided into 
two unequal sections, from either 
of which the compressed air can 
be shut off when carpets narrower 
than the full width of the ma- 
chine are being cleaned. The 
whole of the dust removed from 
the carpets, by the action of the 
compressed air thereon, is drawn away from the machine by an 
air propeller or exhaust fan at the left-hand side ; the dust being 

delivered into a chimney, flue, or other suitable receptacle. 

42 




Fig. 476.— end view. 



658 



COMPRESSED AIR AND ITS APPLICATIONS. 




a. 



PNEUMATIC WORK. 659 

By this method, carpets are cleaned so effectually that any 
amount of beating afterward fails to extract any dust, colors 
are revived, while the fabric sustains no injury whatever. 
Carpets of any description, cloth, and other like materials can 
be similarly cleaned by this process. 

The American Pneumatic Carpet-Cleaning Company has 
plants located in New York City, Chicago, Boston, Philadel- 
phia, Pittsburg, and Cincinnati. 



Chapter XXIX. 



PNEUMATIC WORK— Continued 



PNEUMATIC WORK. 

(Continued.) 

COMPRESSED AIR IN THE BESSEMER CONVERTER AND THE 
BLAST FURNACE. 

In no other industry is the use of compressed air so impor- 
tant a factor as in the manufacture of iron and steel. The blast 
furnace stands first in estimation with its vast volumes of air 
at varying pressures up to 10 pounds or more 
per square inch, and extending in pressure up to 
75 or ioo pounds in operating the Bessemer con- 
verter, and in the lifts and cranes necessary in 
the modern methods in steel manufacture. 

The Bessemer converter and its adjuncts 
require the most precise and delicate handling 
of compressed air of any air power in the manu- 
facturing arts. A slight mistake in handling 
the air valves, or in blowing the melted iron to 
the exact degree to convert it into steel, may involve large 
costs, if not disaster. 




Fig. 478. • 
3emer convert- 



THE USE OF COMPRESSED AIR AT A BLAST-FURNACE PLANT. 

When " A" Furnace of the Maryland Steel Company, Spar- 
row's Point, Md., was blown in for its second blast (November, 
1895), a compressed-air plant was put in, and has been used 
with much success during the past years. Compressed air is 
used for the tap-hole drill, the tap-hole "gun," the transfer 
table at the scales, the turn-table on top of the furnace, and for 
lifting the rails of the turn-table in running off the empty cars. 

The tap-hole drill is a Little Giant rock drill so mounted as 
to swing into place and drill out the tap-hole without any hard 



664 COMPRESSED AIR AND ITS APPLICATIONS. 

manual labor. This arrangement is the device of Superin- 
tendent David Baker, and is described by him in Trans. Amer. 
Inst. Min. Eng. (vol. xxi.) The supporting crane has been much 
changed since that description was written, and now consists of 
a simple and light crane. The crane is fastened to one of the 
columns at the side of the tap-hole so that the drill can be 
swung back out of the way when not in use. The air-pipe is 
connected by swing joints and an expansion sleeve. 

Formerly steam was used to run the drill, but it has several 
disadvantages which air has not. Great care had to be taken 
to prevent the condensed steam from dripping into the iron 
trough and perhaps causing a "boil." The escaping steam 
would make it hot for the men, and the clouds of vapor would 
often prevent them from watching the work well. A hose for 
the exhaust was necessary, and this made another part to care 
for, and it was sometimes burned. In cold weather there would 
be much condensing and loss of power. Compressed air does 
away with all these difficulties. 

The tap-hole gun is S. W. Vaughen's patent device for shut- 
ting the tap-hole by power, thus saving much hard, hot work 
for the men, and doing away with the necessity of taking the 
blast off the furnace after each cast to shut the tap-hole. 

The gun has a breech for loading, a compact valve, and a 
simple and adjustable mounting. It is made of cast iron and 
consists of two cylinders and a piston rod with a piston on each 
end. The air end of the gun. is an ordinary air-cylinder oper- 
ated by a hand-valve. The clay barrel is open at the nose end, 
and has a breech at the other end. The gun is suspended on a 
crane fastened to a column opposite the drill. The crane is 
similar to the drill crane, and the air-pipe has swing joints and 
a rubber-hose connection to allow freedom of motion. 

The gun is loaded with about thirty-five clay balls before 
the cast, and when the iron is all out of the furnace the 
gun is swung around and clamped into place and the whole 
charge shot into the tap-hole at once. By reversing the valve 



PNEUMATIC WORK. 665 

the piston is brought back; the breech is. opened, the clay barrel 
loaded, up again, and more clay shot into the hole till it is com- 
pletely shut up. 

Here the air has the same advantages over steam as in the 
drill. About 65 to 70 pounds air pressure is needed for the 
drill and gun. If at any time there is not enough pressure to 
run the drill well, a signal is given from the furnace to the 
pump-man, and he sets the escape valve of the receiver for 
higher pressure. 

In order to have rapid handling of the ore, limestone, and 
coke, buggies are used, which have four wheels, run on tracks, 
and hold from 1,500 to 2,300 pounds of stock, at the scales; a 
transfer table is placed between the scales and the elevator, 
which is operated by compressed air taken from the blast main 
air-pipe at 10 to 12 pounds pressure. 

COMPRESSED AIR IN A ROLLING-MILL. 

Most of the more successful iron-working establishments 
now use "compressed air" a little — some a great deal; and 
among the foremost of the latter class is the Passaic Rolling- 
Mill Company at Paterson, N. J., not only because of its ex- 
tensive use of compressed air, but particularly by reason of the 
variety of operations performed by it, several of which are of 
more than ordinary interest and originality. 

First a row of jib cranes, each equipped with independent 
air hoist, used for loading the finished material on cars for 
shipment. The air cylinders for this work are about 6 inches 
diameter by 6 feet stroke, mounted on the mast, the air con- 
nection being made with a short piece of hose at the top of the 
crane. 

One of the most interesting applications of compressed air, 
one in which work formerly required the services of thirteen 
men, is now done by four, and with less danger. By it the 
capacity of the rolls has been trebled. This apparatus is not 



666 COMPRESSED AIR AND ITS APPLICATIONS. 

operated entirely by compressed air, steam and air being as- 
signed to the work for which each is considered best suited. 
It consists of two transfer tables, one on each side of the main 
rolls of the rolling mill, the duty of one of which is to deliver 
the heated billet to the first roll, move into position to receive 
it from the second, move and deliver it to the third, and so on 
till the billet comes out a finished beam. Of course the process 
described applies to the table on one side of the rolls only, the 
one on the opposite side operating in the same way with it. 
This transfer table consists of a heavy four-wheeled carriage 
carrying a tilting platform or girder, the top of which consists 
of rollers operated in either direction by bevel gears and shaft. 
The carriage travels in the pit on rails parallel to the rolls in 
moving from one roll to the next, and the end of the tilting 
table next the rolls is raised and lowered to position for the 
upper and lower rolls by an 1 8-inch air cylinder located in a 
yoke. The cross-bend is connected at its centre to the piston 
of this air cylinder and moves the tilting platform by means of 
the side rods fastened to its ends. The action of this cylinder 
is controlled by a special valve, operated from the engineer's 
platform. One engineer and a roll-tender are all that are re- 
quired for the apparatus, and the same number for the other 
table on the opposite side. 

After the beam leaves the rolls it passes to the hot saw, 
where it is trimmed and cut to length. The rollers that carry 
the beam to the saw receive it from the tollers on the transfer 
table, without any handling or even a pause in its motion, so 
that a few seconds after it has received its last squeeze in the 
rolls it is being cut by the saw. This saw is fed through the 
beam by a compressed-air cylinder, which is 12 inches diameter 
by 20 inches stroke; the elastic yet persistent nature of the 
feed given the saw by compressed air is found much better than 
any other method. 

Compressed air performs the next operation on the beam, 
which is to remove it from the rollers (making room for the 



PNEUMATIC WORK. 667 

next) and set it on edge to cool. When the beam lies on the 
rollers after being cut to length the fingers are in a horizontal 
position under it between the rollers, and an air cylinder, 1 5 x 
26 inches, located under the rollers, pulls the fingers to a vertical 
position, bringing the beam with it, at the same time carrying 
it sideways far enough to clear the rollers. 

The rest of the work done by air in these works is being 
done in many places elsewhere, and is consequently of but pass- 
ing interest. There is a busy corner in the bridge shop — a 
group of three riveters, two reamers, a chipping tool and hoist, 
all being operated by compressed air. The total pneumatic 
equipment of the works, outside of the special apparatus de- 
scribed, consists of about 40 cylinder hoists, 12 riveters, 5 drills 
and reamers, and 2 chipping tools. There is also a very inter- 
esting device for charging the heating furnace by compressed 



COMPRESSED AIR FOR BLASTING COAL. 

In endeavoring to dispense with the use of gunpowder and 
other asphyxiating explosives in the deep drifts of coal mines, 
a series of experiments were made in the colleries at Wigan 
and Denton, England, a number of years since, in which air 
was compressed to 946 atmospheres over 14,000 pounds per 
square inch, and conveyed in strong wrought-iron tubes to a 
cast-iron cartridge placed in a drill hole and tamped like a pow- 
der cartridge. The breaking strain of the cast-iron cartridges 
by comparative tests was first ascertained to obtain the proper 
size and thickness, that they might burst at or near some assigned 
pressure, say 10,000 pounds per square inch. Cored castings 
could not be used, or failed from the drifting of the core, caus- 
ing weakness on one side, so as to vitiate many of the experi- 
ments. A size of drilled and turned cartridges was adopted, 12 
inches long, 3^ inches diameter, with walls ^inch thick, hav- 
ing a bore i^f inches diameter. This was found to burst at 
9,500 pounds per square inch pressure. These air cartridges 



668 COMPRESSED AIR AND ITS APPLICATIONS. 

were pushed into close-fitting bores in the undercut coal wall with 
a small pipe attached and tamped the same as with a gunpowder 
cartridge ; the small air pipe was laid to a safe distance to a re- 
ceiver charged at a much higher pressure, when on opening a 
valve the compressed air rushed to the cartridge and an explo- 
sion occurred much in effect like other explosives, and throwing 
down a wall face of from 5 to 6 tons at each blast. The air 
compressor placed at the power station readily compressed the 
air to the required pressure, which was transmitted to strong 
receivers near the working heads, where the operation of charg- 
ing a receiver and a cartridge was readily done by the high- 
pressure valves at the receiver. In this manner the miners 
could carry on the work constantly without having to retire 
from the influence of deleterious gases, and had only to momen- 
tarily shield themselves from flying coal. The ventilating and 
cooling properties of air thus used cannot be too highly praised 
as one of the safeguards in the dangerous work of mining coal 
in the deep and gas-saturated workings of the bituminous coal 
belts. 

Although the expense of blasting by compressed air was 
found somewhat greater than by the use of powder or dynamite, 
this system was proved feasible, but was not continued. It is 
assumed that compressed air yet stands foremost as a substitute 
for the dangerous explosives heretofore used, by the increasing 
depths at which safety is a paramount requirement. 

THE AIR-LOCK SYSTEM IN CAISSON SINKING. 

One of the latest improvements in the use of compressed air 
in sinking the foundations for buildings is the air lock, of which 
the outside feature is illustrated in Fig. 479. It consists of a 
large steel case or chamber containing the air-lock mechanism ; 
a neck extending down a few feet and fixed to the top of the 
wooden caisson by a flange; a platform at the top as a footing 
for the men operating the caisson valves, and the hoisting of the 



THE AIR-LOCK SYSTEM IN CAISSON SINKING. 



669 



excavated material. This system enables an ordinary .bucket, 
or even a barrel of cement, to be passed in and out of the cais- 
son without detaching it from the hoisting-rope leading to the 
derrick. The lock has a simple lower door hinged on a shaft, 
which shaft extends to the outside of the lock through a stuf- 
fing box. On the outside 
is a counter weight lever 
and counter-weight, to bal- 
ance the door and afford 
means of operating from 
the outside. Above the 
lower door is a cylindrical 
section, called the bucket 
chamber, large enough to 
contain the bucket. The 
opening above the bucket 
chamber, instead of being 
closed by a single door, is 
closed by two doors work- 
ing to and from the centre. 
When these doors are 
shut they completely close 
the opening, and form 
a tight joint with each 
other, with the exception 
of a small opening at the 
centre. In this small 
opening at the centre fits 
a stuffing-box of simple 

design, through which the hoist-rope passes. The two doors 
then close around the rope contained in the stuffing-box and 
completely prevent the escape of air through the opening, 
while permitting the rope to pass freely. As soon as the bucket 
is filled in the working chamber an electric bell rings above, 
and the engineer at the derrick hoists the bucket into the; bucket 





67O COMPRESSED AIR AND ITS APPLICATIONS. 

chamber. The lower door is then closed, a valve is opened 
permitting the air in the lock to escape, the upper doors are 
then opened, and the bucket is hoisted out, 
the stuffing-box remaining on the rope just 
above the bucket. In returning, the opera- 
tions are reversed. 

The caisson is an excavating machine, as 
well as a foundation, and must be considered 
in that light. 

The side elevation (Fig. 480) shows the 
air lock at the top, with the levers L L ' and 
their counter-weights W W\ below which is 
the elevator or air .shaft, with the ladder, as 
shown, and at the extreme lower part is the 
air chamber. The openings M and iVare re- 
spectively for the air pipe and the whistle con- 
nection, as shown in the cut Fig. 480. The 
illustration Fig. 481 gives the details of the 
internal arrangement. 

Referring to Fig. 481, the upper swinging 
gates, A and A 1 , turn about the centre, O, 
being counter weighted by Fand V\ These 
are worked by the handle L, both gates swing- 
ing on the centres D and H. 

When the upper gates have been moved 
to the open position, so as to come at rest on 
the lugs B and B\ the buckets can be moved 
in or out of the air chamber. The meeting 
edges of these, as well as the lower gates, 
are packed with rubber tongues, so as to make 
air-tight closures. The lower swinging gates 
are worked in the same manner, being opened and closed by 
the lever L \ and counterweighted by IV 1 (Fig. 480). 

The successive operations are as follows: The bucket is 
lowered into the air lock, the upper gates being open and the 




Fig. 



3.— side VIEW. 



THE AIR-LOCK SYSTEM IN CAISSON SINKING. 



6; i 



Ilnixlinrj Cable^ 



lower ones closed. The upper ones are then closed and air is 
admitted from the air shaft until the pressure equals the press- 
ure in the air chamber. The lower gates are then opened and 
the bucket descends into the shaft and finally into the caisson 
chamber. 

There is a three-way valve, which serves three purposes: 
First, it permits air to escape from the air lock; second, it 
equalizes the pressures in the air 
chamber and the air lock, and, 
third, it prevents the escape of air 
from either. It is regulated by 
means of contact wheels, which in 
turn are moved by connecting with 
the handle L by means of a rod 
not shown in the figures. When 
the upper gates are closed the 
motion of the lever simultaneously 
closes the air exhaust from the 
air lock and makes connection 
with the air chamber below, thus 
equalizing the pressure in the two 
chambers. A thumb-latch locks 
these doors in both the open and 
in the closed position. The ar- 
rangement of the lower swinging gates prevents their move- 
ment until the pressures in the upper and lower chambers have 
been equalized. 




""& ' Lower Swinging Gates Ijj 



AIR-LOCK CHAMBER 



Chapter XXX. 



THE PNEUMATIC SYSTEM 
OF TUBE TRANSMISSION 



THE PNEUMATIC SYSTEM OF TUBE 
TRANSMISSION. 

The earliest suggestion and experiment in the work of 
transmission in tubes was made by Dr. Papin in the seven- 
teenth century, since which its usefulness lay dormant through 
the centuries until 1853, when the first successful pneumatic- 
tube system was put in operation in London, England, with a 
i-i-inch tube 650 feet long. It was operated by a vacuum and 
again extended in 1858 with 2-|--inch tubes. From this on, the 
system has grown rapidly, and London has 34 miles of despatch 
tubes with 42 stations; the transmission power being by both 
compression and exhaustion. It has also extended its useful- 
ness in the large cities of England and on the Continent. In 
Berlin, Germany, the transmission of telegraph messages by 
pneumatic tubes commenced in 1865. There is quite an inter- 
esting history of the experiments in transmission of passengers 
and goods by this system, covering many years of trial, but, as 
it has not proved successful, we pass it by. Its most success- 
ful score is in the store cash system, the telegraph despatch, 
and the later postal-transfer system. 

Its first introduction on the larger scale was made in Phila- 
delphia in 1893. A six-inch main was laid to connect the main 
post-office with the Chestnut Street branch, a distance of nearly 
a mile. 

On account of the large size of the pipes compared to those 
used in the European system, the capacity of this plant was 
much greater. The area of the tubes was increased many 
times, and of course the carriers were correspondingly larger. 
The speed of the Philadelphia system was, moreover, doubled, 
and it had improved appliances for receiving and transmitting. 



6y6 COMPRESSED AIR AND ITS APPLICATIONS. 

This plant was opened in 1893 and has been operated success- 
fully ever since. 

The air current flows continuously from the main post-office 
to the Bourse through one tube and returns to the main post- 
office through the other, thus forming a loop with the return 
end connected to the suction pipe of the compressor at the post- 
office. There is an opening in the tube to the atmosphere near 
where it is connected to the compressor, so that the entire cir- 
cuit contains air at a pressure above the atmosphere. It is a 
pressure system rather than a vacuum system, as these terms 
are commonly understood. 

Carriers occupy sixty seconds in transit from the post-office 
to the Bourse, and fifty-five seconds for the return trip. The 
carrier is only 18 inches long; but each carrier has a capac- 
ity of 200 letters, and they can be despatched at six-second 
intervals, making the tube capacity 240,000 letters per hour, 
including both directions. The actual speed in practice is about 
52 feet per second, in the Philadelphia service, and in the first 
four years it was in use it is estimated that more than 35,000,- 
000 letters were despatched through these tubes, with but one 
serious interruption due to an obstruction in the tubes. 

It was determined for the New York system to make the 
tubes of larger capacity than those used in Philadelphia, and to 
maintain a working speed of thirty miles an hour under a head- 
way of twelve seconds. The line to the Produce Exchange is 
nearly 4,000 feet long and consists of two tubes, side by side, 
8 inches in diameter, and about 5 feet below the surface. One 
is used for outgoing and the other for incoming mail, they being 
connected at the sub-station by a loop. A powerful compressor 
forces the air into the outgoing tube at a pressure of 7 pounds 
to the square inch. On account of its elasticity, it flows through 
the pipe with an increasing velocity, but by the time it reaches 
the sub-station the pressure has fallen just one-half. From 
here the current returns by the second or return tube, and as it 
enters the receiving tank its pressure is equal to that of the 



THE PNEUMATIC SYSTEM OF TUBE TRANSMISSION. 67? 

atmosphere. This tank is joined to the suction pipe of the 
compressor, and as the two lines are connected by a loop at the 
other end, there is a continual circulation of air throughout. 
The pipes are of cast iron with a very smooth interior finish. 
All bends are of at least 8-feet radius and made of seamless 
brass with a diameter of not less than 8f inches on the inside. 

The current is continuous from the starting of the compres- 
sors in the morning until they stop at night, so it was necessary 
to have some means by which the carriers could be inserted and 
removed from the line without interfering with the flow of air. 
This is done by means of a transmitter and receiver, one at 




Fig. 482.— sending apparatus and receiver, new york post-office. 

each station. The former consists of a piece of 8-inch pipe, 
long enough to enclose the carrier. It is hung on a shaft, over- 
head, so that it can be swung out from the main line to receive 
the carrier and then moved back into position where the current 
forces the latter into the main tube. The ends are smoothed 
off square so that no air can escape at the joints. When this 
section is swung out of line two projecting plates move across 
the ends of the opening and shut off the air, the current mean- 
while going around by means of a connection. When the trans- 
mitter is not in use the movable section is drawn over to the 
loading tray and the air goes through the U-shaped by-pass. 
When a carrier is to be sent it is placed in the tray and pushed 



678 



COMPRESSED AIR AND ITS APPLICATIONS. 



into the transmitter; then, by pulling a lever, the latter is 
swung into position and the carrier is forced out. An automatic 
time-lock prevents them being sent with less than twelve sec- 
onds headway, thus insuring a proper distance between them 
in the tube. When the carriers arrive at the sub-station the 
pressure of the air is 3-^ pounds to the square inch, so the tube 
cannot be opened to remove them. They also have a velocity 
of about thirty miles an hour, and some means had to be pro- 
vided for gradually 
checking their speed. 
These two things are 
accomplished by means 
of a closed receiver, 
which consists of an 8- 
inch cylinder 4 feet in 
length. In its normal 
position it forms a con- 
tinuation of the tube by 
which the carrier ar- 
rives, and on entering 
the receiver it com- 
presses the air in front 
and is stopped without 
any shock. There are 
a number of openings in the pipe just in front of the receiver 
connected with the other or returning line by which the current 
continues back to the main station. The compressed air in the 
receiver opens a small valve and thus keeps the carrier from 
being thrown back into the main tube. The receiver is auto- 
matically discharged in three or four seconds by a piston, which 
tilts it to an angle of 40 . The carrier slides out onto an in- 
clined platform which is kept in position by a counter-weight. 
The weight of the carrier, however, overbalances this and 
causes it to drop to a horizontal position, and the carrier is 
thrown out on to a table in front of the operator. This piston 




Fig. 483 



SENDING APPARATUS AND CLOSED RE- 
CEIVER AT A STATION. 



THE PNEUMATIC SYSTEM OF TUBE TRANSMISSION. 679 

is worked by compressed air supplied from the receiver. Above 
the front end of the- receiving chamber is a plate, arranged so 
that it comes down and closes the end of the main tube when 
the receiver is tilted to be discharged. 

The transmitters at both ends of the line are the same, but 
the receiver at the main office is different from the one at the 
sub-station. At this end it consists of a section of the end of 
the tube closed at the rear by a gate. The air, now expanded 




Fig. 484.— section of sending apparatus. 

to the same pressure as the atmosphere, passes from the tube 
through openings, four feet in front of the receiver gate, down 
to the tank in the basement. The momentum of the carrier is 
checked in compressing the air in the chamber after it has 
passed these openings. Part of this compressed air operates a 
piston which opens the gate mentioned above, then the small 
pressure of air forces the carrier out on to the receiving table. 
If there is not sufficient pressure to expel it, the openings can 
be partly closed by means of a valve. As it passes out, it hits 
a small finger which causes the gate to be closed. 

Intermediate stations are usually supplied with cut-out 



68o 



COMPRESSED AIR AND ITS APPLICATIONS. 



switches, so that carriers can be sent directly past the station 
without entering it. These switches are moved by air pressure, 
controlled electrically from the nearest station (see Fig. 485). 

There is no part of this system that has been the object of 
more thought and study than the carrier that contains the mail 
or other material to be transported. It is made of a seamless 
steel tube 23^- inches long, closed at the front end by a sheet 
metal head and buffer, and closed at the rear end by a hinged 
cover provided with a lock (see Fig. 486). The right-hand 
carrier is of the New York system. 

The body of the carrier is about an inch smaller than the 
tube through which it travels, the space between the body of 




Fig. 485.— cut-out switches from main line. 



the carrier and the surface of the tube being filled by two 
fibrous rings that serve not only to prevent the escape of air 
past the carrier, but as wearing surfaces to slide on the lower 
side of the tube. These bearing rings are made of cotton fibre, 
and they will endure until the carrier has travelled about 5,000 
miles, when they become worn so small that they have to be 
replaced by new ones. A carrier weighs 13I pounds and will 
contain 600 ordinary letters. 

In Fig. 486 is represented the comparative sizes of the car- 
riers used in the progress and expansion of the pneumatic 




THE PNEUMATIC SYSTEM OF TUBE TRANSMISSION. 68 1 

transmission system. No. i to the left is the carrier used in 
the Berlin system; No. 2, the largest carrier used in the Lon- 
don system; No. 3, a six-inch carrier of the Philadelphia sys- 
tem ; No. 4, an eight-inch carrier of the New York and Boston 
systems. No. 2 is also 
the comparative size of 
the New York telegraph 
despatch system. 

LOCATION OF OBSTRUC- 
TIONS BY LODGMENT OF 
A CARRIER. 

Considerable appre- 
hension arose from the fffi 
accidental lodgment of a $ I 

carrier in the Philadel- jfl H ]H 
phia tube, and also later ^ " "" — 

in the New York and T 
Brooklyn post-office line. 

The plan was to disconnect the terminal apparatus at one 
of the stations, fire a pistol into the tube, and note the time 
that elapsed between the discharge of the pistol and the return 
of the sound as an echo reflected back from the obstructing 
carrier; then, knowing the velocity of sound, a simple calcula- 
tion would give the distance from the station to the carrier. 

A chronograph improvised for registering the time consisted 
in part of a metal cylinder or drum 10 inches in diameter, which 
could be revolved by a hand crank and which would move end- 
wise very slowly when in rotation. The polished metal surface 
was coated with smoke, and therefore a motionless pin-point, 
in contact with the drum, would trace a fine spiral line thereon. 
The point was not motionless, though. It was attached by a 
horsehair and sealing-wax to one prong of a tuning-fork giving 
the musical note C, and therefore vibrating 512 times per sec- 
ond. Consequently 512 waves per second were imparted to the 



Fig. 486.— the carriers. 



682 COMPRESSED AIR AND ITS APPLICATIONS. 

trace ; and these were large enough to admit of division into 
quarters. Another disturbance of the point was caused elec- 
trically by a pendulum of a clock beating half-seconds. Each 
beat made a short, sharp projection sideways on the wavy line. 
Hence, the complete half-seconds could be counted by these 
marks, while the time interval remaining after the last pendu- 
lum beat could be ascertained from the tuning-fork waves. 

Finally, provision was made for automatically recording on 
the cylinder the instant of the original shot and also of the 
arrival of the echo. A vibrating diaphragm close to the drum 
bore another stylus or sharp point, and this diaphragm was so 
sensitive that, when struck by sound, it would move enough to 
make a scratch on the sooty surface. 

Five trials were made with this apparatus, and the mean of 
the observations gave 2.793 seconds as the time required for 
the sound to travel both ways. A velocity of 1,093 feet was 
assumed for a temperature of 32 , and a correction of 1.12 feet 
per second for each degree above that standard was applied. 
The observed temperature down in the ground was 39 . The 
computed velocity was 1,101 feet, and the estimated distance, 
counting both ways, was therefore 3,075 feet. Dividing by 
two, the explorers made the actual distance of the box 1,537 feet 
from the open end of the tube. This was more than a quarter 
of a mile off. When workmen dug down at the designated 
spot, several blocks away, they found the box within a foot or 
two of the place. A break had occurred in the pipe about 
twenty feet further away, but the obstruction was found exactly 
where calculation located it. 

THE ENGLISH TUBE SYSTEM. 

Some computations have been made by English experts on 
the power required to operate a pneumatic-tube system of 
2\ and 3 -inch tubes which is applicable to the larger tubes in 
the ratio of their comparative areas. 

" The pneumatic tubes used in Great Britain are made of 



THE PNEUMATIC SYSTEM OF TUBE TRANSMISSION. 683 

lead, and when laid beneath the streets they are enclosed in 
iron pipes for protection. The tubes vary in length from two 
miles downward, the average length being about three-fourths 
of a mile. The diameter of the longer and more important 
tubes is 3 inches, and that of the shorter and less important 
tubes 2\ inches. The carriers within which the messages are 
sent through the tubes are made of gutta-percha tubing, cov- 
ered with felt, and have a head of several pieces of felt which 
accurately fits the tube. The carriers used with the 3-inch 
tubes weigh about 7 ounces, and will contain about thirty-six 
messages; those used with the 2i-inch tubes weigh about 2\ 
ounces, and will contain about twelve messages. 

" Each of the tubes is provided with a simple electrical con- 
trivance by which the departure from and the arrival at each 
station of the carriers is signalled. 

" The power by which these tubes are worked is derived 
from steam engines located at the central office. These engines 
work air pumps which either take air from the atmosphere and 
compress it to a smaller volume and then discharge it into the 
pressure main, whence it is admitted by means of taps into the 
different tubes when carriers are despatched to an out-station — 
or the pumps take air from the vacuum main, compress it to 
the atmospheric pressure, and then discharge it into the atmos- 
phere; the air in the vacuum main is, of course, being contin- 
ually renewed by the air which flows from the atmosphere 
through the tubes into the vacuum mains during the transit of 
the carriers from the out-stations. 

''The velocity with which the carriers travel is usually be- 
tween one-third and one-half a mile per minute. The approxi- 
mate time of transit in minutes through a tube of L miles = 
2.7 U with the 2^-inch tube, and 2.1 U w T ith the 3-inch tube. 

" The energy expended in driving a carrier from the cen- 
tral office to an out-station is equal to the volume of compressed 
air which flows into the tube during the transit multiplied by 
the work required to produce a unit volume of compressed air. 



684 COMPRESSED AIR AND ITS APPLICATIONS. 

" The volume of compressed air which flows into the tube 
during transit is equal to about six-sevenths of the tube's cubical 
capacity. The capacities of the 2\ and 3-inch tubes are 146 
and 25 1 cubic feet per mile respectively, so that the volumes of 
compressed air used in driving a carrier through a mile of each 
tube are 125 and 200 cubic feet respectively. 

" The work required to produce a cubic foot of compressed 
air at a pressure p x from a pressure p lies between the isother- 
mal value 

0.01005 Pi l°g- — horse-power minutes, (1) 

and the adiabatical value 

( (v> \ ' 29 ) 

0.01505 pj < (ii 1 ) — i - horse-power minutes. (2) 

So that to produce a cubic foot of compressed air at a press- 
ure of 12 pounds to the square inch above the atmospheric 
pressure would require between 0.0695 and 0.0755 net horse- 
power minute, or say about 0.085 gross horse-power minute; 
and, therefore, the energy expended in driving a carrier through 
a mile of the i\ and 3-inch tubes would be 10.6 and 17 horse- 
power minutes respectively. 

" When a carrier is despatched from an out-station to the 
central office, the air in the tube first expands into the vacuum 
main and thence into the pumps, where it is compressed to the 
atmospheric pressure and then discharged into the atmosphere. 
By the aid of formulas 1 and 2, it is found that the gross amount 
of work of 0.065 horse-power minute is required to pump a 
cubic foot of air into the atmosphere from a vacuum main at a 
pressure of 8 pounds per square inch below the atmospheric 
pressure. If the tube has been at rest immediately before the 
carrier is despatched to the central office, the volume of air 
which will be pumped into the atmosphere from the vacuum 
mains will be equal to the cubical capacity of the tube; and, 
therefore, the energy expended in the transmission of the car- 
rier would be 8 and 13 horse-power minutes with 2\ and 3-inch 



THE PNEUMATIC SYSTEM OF TUBE TRANSMISSION. 685 

tubes respectively. If, however, the tube had immediately 
previously been used to receive a carrier from an out-station, 
there would be a partial vacuum in the tube, and, therefore, 
the expenditure of energy would be less, say 6-| and ioi horse- 
power minutes respectively. But if, on the other hand, the 
tube had just previously been used to despatch a carrier to an 
out-station, it would be partially filled with compressed air; 
and the amount of work which the pumps would have to per- 
form would be greater, and the amount of energy expended 
during the transit of the carrier would be about 12 and 19 horse- 
power minutes with the 2\ and 3 -inch tubes respectively. 

" These amounts of energy would be expended in several 
different forms. First, work would be performed in pushing 
back the atmosphere at that end of the tube at which the press- 
ure was lowest; secondly, energy would be expended in gen- 
erating mechanical vibrations of the tube; and, thirdly, in over- 
coming the friction of the carrier within the tube. The first of 
these quantities is much the greatest, and is equal to about 
three-fourths the net work of the engine in pressure working, 
or about two-thirds the net work of the engine in vacuum 
working. 

" The energy expended in overcoming the friction of the 
carrier may be approximately calculated from the formula 

■ horse-power minutes, where W is the weight of the car- 

150 

rier in ounces and L length of tube in miles. 

"Thus, with the 2i-inch tube, the energy expended in over- 
coming the friction of the carrier through a mile of tube would 
be about -fa horse-power minute, or with the 3 -inch tube about 
^q horse-power minute. So that the energy expended in over- 
coming the friction of the carrier itself would be only -%^ to 
■g-^-Q- of that expended in expelling the air from the tube." 

The mail-tube industry has now developed so fast in this 
country that even 8-inch tubes, with cartridges carrying six 
hundred letters, are in successful operation in our big cities. 



686 



COMPRESSED AIR AND ITS APPLICATIONS. 



The longest circuit ever built in the world is in the main line 
recently laid in New York City, extending from the terminal 
post-office, a distance of three and one-half miles. This is an 
8-inch tube circuit. The cartridges travel 
at tremendous speed, the time of transit 
consumed in either direction being only 
seven minutes. Another big circuit has 
been laid across the Brooklyn Bridge, so 
that you may have the pleasure of knowing 
that while you are speeding over the bridge 
in the cars, your mail may be making bet- 
ter time ahead of you, shooting away in 
the cartridge inside the big tube like an 
8-inch projectile. 



COMPRESSED 



AIR IN STORE 
SERVICE. 



AND OFFICE 



The pneumatic lift is one of the mod- 
ern conveniences for the quick transmis- 
sion of packages and light goods — in fact, 
a perfect compressed-air dumb-waiter ser- 
vice for our high buildings. 

There are five air lifts in The World 
building, one of which runs up through 
the entire building, by which an immense 
business is transacted in transmitting copy 
and orders. 

As will be seen in Fig. 487, a cylinder 

is employed which is equal in length to the 

range of motion of the car. On account 

of its length it is small in size, and can be 

placed in the elevator well. The suspender 

rope of the car passes directly into the cylinder, and is attached 

to the piston. The rigid piston is thus avoided, and therefore 

no doubling blocks or multiplying gear are required. The 



FIG. 487 —PARCEL LIFT. 



THE PNEUMATIC SYSTEM OF TUBE TRANSMISSION. 



68; 




>^mim%> 



FIG. 488.— PNEUMATIC ELEVATOR AND TUBE TRANSMISSION. 

For stores and office buildings. System of the Miles Pneumatic Tube Company, 
1223 Broadway, New York City. 



688 



COMPRESSED AIR AND ITS APPLICATIONS. 



piston lifts the car by a force of compressed air let into the 
cylinder by a valve. The compressed air is supplied from a 
pressure tank, automatically regulated, precisely as it is for the 
operation of despatch tubes. Hence a system of tubes and 
light elevators can be operated from the same pressure tank. 

The pneumatic elevator and system of pneumatic-carrier 
tubes converging to a central station are all operated from the 
same air-pump and receiver. 

In this system, when the tubes are not in actual use making 




Fig. 489.— the counter station. 

transmissions, they are open at both ends to the atmosphere, 
and can be used as speaking-tubes. They are in use in some 
of the largest buildings in our cities, notably the Waldorf- 
Astoria Hotel. Single lines are in use 1,200 feet between ter- 
minals. 

The counter station (Fig. 489) is used for store service and 
office counters, showing tube, terminal, and metallic hood. The 
valve is released by an electro-magnet, which throws the catch 
off the cover and is operated by a key at the other terminal. 

Fig. 490 shows the operating mechanism of the automatic 



THE PNEUMATIC SYSTEM OF TUBE TRANSMISSION. 



689 



terminal valve and its air-pressure lock. As soon as the car- 
rier is expelled from the tube, the closed cover automatically 
opens to the position shown 
in the valve represented on 
the left-hand side of the cut. 
The pressure is automatically 
shut off by the opening cover, 
and the tube is then open at 
both ends to the atmosphere, 
and stands ready to transmit 
carriers from either end to the 
other' end, and while not in 
actual use it consumes no 
power. The tube can open 
downwardly at the ends, or 
upwardly, as shown in the 
hand-operated terminal (Fig. 
491). The adjacent connec- 
tion with the pressure-supply pipe is opened by shutting the 
cover, and automatically is held open while the cover remains 




Fig. 490.— automatic terminal valve. 




-F^ND-OPERATED TERMINAL VALVE. 



44 



69O COMPRESSED AIR AND ITS APPLICATIONS. 

closed. The air pressure running freely into the tube forces 
the carrier immediately through the tube. 

In Fig. 492 is represented an automatic terminal of a store 
or office pneumatic despatch or cash-carrier tube with a catch 
basket. The cover is thrown open which closes the air-press- 
tire inlet of the supply pipe and is ready for the ejection of 





Fig. 492.— automatic terminal. 
With catch basket. 



Fig. 493.— floor station. 



the tube messenger or carrier. The small cylinder at the right 
contains a piston with a projecting rod that unlocks the cover 
catch by the air pressure when the carrier passes cross-connec- 
tion and is approaching the valve. 

In Fig. 493 is shown a floor-stand which is also the air-press- 
ure pipe, with the carrier pipe dropping from the ceiling and 
discharging into a basket. It has an electric automatic opening 
device and lock attached. 



THE PNEUMATIC SYSTEM OF TUBE TRANSMISSION. 



69I 




Chapter XXXI. 



COMPRESSED AIR IN 
WARFARE 



693 



COMPRESSED AIR IN WARFARE. 

THE PNEUMATIC DYNAMITE GUN. 

After many years of experiment in the fruitless endeavor 
to throw a dynamite torpedo from a gun with powder or other 
explosive, Mr. D. M. Mefford, of Ohio, seems to have been the 
first to indicate the correct solution of the problem, by applying 
compressed air as the propelling force in his pneumatic dyna- 
mite gun. The first gun, which was of 2-inch bore by 28 feet 
in length, was tested by Lieut. E. L. Zalinski in New York 
harbor in 1884, using an air pressure of 500 pounds. A range 
of one and one-quarter miles was obtained with an accuracy and 
precision surprising when the crude method of construction and 
the handling of the air valve is considered, which latter was 
largely due to the personal equation of the gunner for different 
discharges. 

Encouraged by the success of these experiments, a 4-inch 
gun was built, in which air pressure at 1,000 pounds per square 
inch was used, and in which an improved form of air valve was 
made automatic in action and capable of delivering uniform 
amounts of air. In experiments with this gun the practicabil- 
ity of throwing dynamite cartridges with an air pressure of 
1,500 pounds per square inch was settled beyond dispute. 

During these experiments Lieutenant Zalinski developed 
the electric fuse, which largely contributed to the efficiency of 
the gun. An 8-inch gun, 60 feet in length, capable of throw- 
ing a shell containing 100 pounds of explosive to a distance of 
two miles with an air pressure of 1,000 pounds, was then built 
and mounted at Fort Lafayette in 1885 ; which we illustrate in 
Fig. 495, giving a general view and details. 

To secure rigidity of barrel it is mounted on a truss, the 



6 9 6 



COMPRESSED AIR AND ITS APPLICATIONS. 




H ft 

l -s 



COMPRESSED AIR IN WARFARE. 697 

whole turned upon the breech trunnions in the act of elevating 
by means of a ram acting against the heel plate of the truss. 
The trunnions rest in two hollow upright castings supported 
upon the chassis. The castings also act as air connections be- 
tween the eight 12 -inch by 2 2 -feet tubes forming the firing res- 
ervoir, said tubes being secured on chassis and turning with it. 
The chassis is a front pintle arrangement similar to those in use 
for heavy powder guns. 

Upon the chassis are also mounted the cylinders for giving 
side train. 

The air supply from the magazine reservoir into which the 
compressors deliver, is carried through the pintle around which 
the gun trains, into the firing reservoir mounted on the chassis. 

The firing valve, placed in the head of one of the trunnion 
supports, is capable of adjustment, to cut off the air at any 
desired point in the barrel for varying ranges. It should be 
borne in mind that at each discharge only a small per cent of 
the air in the firing reservoir is used, and if desired the orig- 
inal pressure of 1,000 pounds can be immediately restored while 
loading for the next shot, by opening the connection between 
the firing and the magazine reservoirs, the latter always being 
maintained at a higher pressure. By this method the firing 
can take place as rapidly as the shell can be loaded and. the gun 
aimed ; the best record for speed being the discharge of five 
projectiles in nine minutes and forty seconds. 

The system is also capable of greater accuracy (within the 
limits of its range) than powder guns ; the initial pressure in 
powder guns varying with the condition and age of the powder 
and temperature of gun at instant of firing; whereas, in the 
pneumatic gun, with a known initial pressure and point of cut- 
off, the resulting range must necessarily be constant for any 
given weight of projectile and degree of elevation. 

The fact that the gunner has under his immediate personal 
control all movements necessary to bring the gun to bear on 
the enemy without removing his eye from the sight increases 



698 COMPRESSED AIR AND ITS APPLICATIONS. 

the speed with which accurate shots can be delivered. The 
8-inch gun was worked constantly, for experiment and exhibi- 
tion, at 1,000 pounds pressure for sixteen months, delivering in 
that time a greater number of shots than it would be possible 
to fire from a powder gun without either destroying or render- 
ing it unserviceable. 

At an elevation of 35 , shells containing 60 pounds of explo- 
sives have been repeatedly fired 2\ miles ; and at an elevation 
of 33 , shells containing 100-pound charges have attained a 
range of 3,000 yards. 

In the lower left-hand corner of the cut (Fig. 495) is shown 
the section of the detonator at the point of the shell. The fuse 
B contains an electric battery in the small case O, composed of 
chemicals in a dry state. The battery has a penetrating point, 
P, which when driven in contact with the insulated plunger M 
N, to which the circuit wire O is connected and the circuit com- 
pleted through the circuit-breaker, fires the cap at C in the rear 
of the charge. There is much detail in the arrangement not 
necessary to explain here, by which the shell is exploded on a 
time circuit or by impact upon the hull of a vessel. 

In Fig. 496 is illustrated the pneumatic gun invented by 
Lieut. J. W. Graydon, U. S. N. It differs from the Zalinski 
gun in being very much shorter and designed to be operated 
under a pressure of 3,000 pounds per square inch. In a field- 
piece as shown in the cut the high-pressure air bottles or cylin- 
ders are fixtures of the gun and carriage, and have air capacity 
for the discharge of a number of shots. 

The capacity of the bore of a 3 -inch field-piece, 10 feet in 
length, would be something less than a half cubic foot, includ- 
ing the projectile, and would require less than a fourth cubic 
foot of compressed air for discharging a projectile at 1,500 
pounds air pressure. A battery of six bottles 4 inches in diam- 
eter and 5 feet in length would contain enough air at 3,000 
pounds pressure for twelve shots. 

Another form of pneumatic gun was brought out by Mr. Dana 



COMPRESSED AIR IN WARFARE. 699 

Dudley, the "Powder Pneumatic Gun," in which the air was 
compressed at the moment of firing by a powder charge ; thus 
dispensing entirely with the ponderous air-compressing machin- 
ery and better adapting the gun to field service for firing tor- 
pedoes. It consists of a gun barrel of light weight connected 
at the breech with a tube of similar bore reaching forward and 
connecting with a stronger tube all lying parallel with and be- 
neath the gun. A torpedo is placed in the breech of the gun 
just beyond the air inlet, and a powder charge in the explosion 
tube just beneath the gun breech. On firing the powder charge 
the air is compressed in the forward part of the firing chamber 




Fig. 496.— the graydon pneumatic gun. 



and in the connecting tube, generating a pressure of from 800 to 
1,000 pounds per square inch. The force of the explosion, cush- 
ioned by the two columns of air intervening between the powder 
and the projectile in the central tube, acts upon the projectile. 
With a slight noise and without a particle of smoke or flame 
the projectile is driven out of the barrel and passes smoothly 
through its trajectory. About the same effect is attained as 
with the regular pneumatic gun. The extensive air-compress- 
ing plant of the latter is, in the case of the Dudley gun, repre- 
sented by a simple blank cartridge. 

Compressed air is now used for controlling the recoil of 
guns and mortars, and in the operation of loading, elevating, 
and traversing mortars and guns in fortifications it has been 
proved effective and a most convenient and labor-saving ele- 
ment in the operating of engines of war. 



700 COMPRESSED AIR AND ITS APPLICATIONS. 



COMPRESSED-AIR SYSTEM ON THE UNITED STATES MONITOR 
"TERROR." 

The use of compressed air as a motive power on board a 
warship presents several advantages over steam or hydraulic 
power, which renders it a powerful competitor. As compared 
with steam, it is less dangerous, especially during an action, 
when a broken steam-pipe might prove terribly fatal, and it 
enables certain parts of the ship to be kept at an even tempera- 
ture which would otherwise be rendered uncomfortably hot by 
the presence of steam-piping. Steam and hydraulic engines, 
moreover, require exhaust pipes discharging outside the hull of 
the ship; whereas the exhaust from the pneumatic cylinders 
may be turned into the ship or into the outside air, as may be 
most convenient. There are certain localities in a ship where 
the exhaust from a pneumatic engine would prove a valuable 
source of ventilation, as, for instance, in a turret crowded with 
men and machinery, or in the close confinement of a steering 
room situated below the protective deck. As compared with 
hydraulic power, the compressed-air system is cleaner and 
more convenient, and free from the discomfort that arises from 
the leaking of hydraulic pipes and cylinders. 

In 1890 the Navy Department authorized a complete pneu- 
matic system for steering the monitor Terror and operating her 
turrets. Owing to delays in the completion of the ship, the 
new system was not tried until late in 1896, when the whole of 
the elaborate plant was put to a thorough test at sea, and gave 
the greatest satisfaction to the naval experts. As the Terror 
was the first vessel in the world to be so equipped, there was 
considerable anxiety as to the success of the experiment ; but 
now that the plant has demonstrated its ability to do all that 
was claimed, its success has stimulated the use of compressed 
air in similar lines in the navies of Europe. 

Directly below the centre of the turret is a pneumatic load- 



COMPRESSED AIR IN WARFARE. 



/OI 



ing machine, which rotates upon a vertical shaft, and may be 
swung to the right or left as desired. The 500-pound shell 
and the cartridge, the latter in two parts, are run out from their 
respective rooms on a overhead trolley and placed in the tray 
of the loading machine, as shown in Fig. 497. The tray is 
pivotally attached to the body of the machine by a set of par- 




FlG. 497.— AMMUNITION ELEVATOR AND PNEUMATIC LIFT FOR LOADING THE ELEVATOR. 



allel rods and a lever which carries at its inner end a circular 
rack. Above the rack is an air cylinder whose piston rod ter- 
minates in a vertical rack which engages the circular rack. By 
admitting air at the top of the cylinder, the tray with its load 
is raised to the required height and the latter is placed in the 
pockets of the loading car. 

There are two of these cars, one for each gun, and they 



702 COMPRESSED AIR AND ITS APPLICATIONS. 

travel upon two vertical hoists or trackways which lead up to 
the breech of the guns. The hoisting is done by two pneu- 
matic cylinders located on the floor of the turret between the 
guns. Attached to each piston rod and beneath each cylinder 
is a set of multiplying sheaves. Over these passes a wire rope, 
one end of which is fastened to the floor of the turret, the other 
end being carried to the loading car. The speed of the rope 
is so adjusted that the full stroke of the pistons will serve to 
hoist the loading car from the floor of the handling room to 
the breech of the gun. 

By reference to Fig. 497, it will be seen that the loading 
car contains three parallel pockets, which rotate within the 
frame of the car, friction wheels being interposed to facilitate 
the movement. One of the pockets carries the shell and the 
other two the powder charge. The car is automatically brought 
to a stop with the lowest pocket containing the shell imme- 
diately in line with the breech of the gun. 

It is then pushed home by a telescopic rammer which is 
operated by compressed air, the valve which admits the air 
being worked by a man who sits astride of the cylinder (Fig. 
498). It will be noticed that the rammer is carried by a bracket 
bolted to an extension of the gun carriage, and it is conse- 
quently held at all times in true line with the bore of the gun. 
After the shell has been rammed home, the loading car is rotated 
and the two sections of the powder cartridge are brought suc- 
cessively opposite the breech and pushed home. The breech 
plug is then swung round, thrust into place, and locked. 

The air for driving the various pneumatic devices is com- 
pressed by two separate engines, one being placed in the hold 
near the forward turret and the other near the after turret on 
the berth deck. The working pressure is 125 pounds per 
square inch, and there is no reservoir for the air except an 
8-inch pipe, which runs through the vessel and supplies the two 
turrets and also the steering device in the steering-room at the 
extreme after end of the ship. These two engines supply suffi- 



COMPRESSED AIR IN WARFARE. 



703 



cient air for turning the turrets, elevating the guns, lifting the 
ammunition into the cages, raising the cages to the breech of 
the gun, ramming home the charge, closing the breech, check- 
ing the recoil, and, lastly, and most important operation of all, 
steering the ship itself. 

The two turning engines are placed upon the floor of the 
turret, one on each side of the big guns. Each engine has two 




Fig. 498.— charging the gun ; the loading car is between the telescopic rammer 
and the breech of the gun. 



cylinders, 8 inches in diameter by 14 inches stroke. A worm on 
the crank shaft operates a set of gears by which the power is 
multiplied many times over before it reaches a driving pinion, 
which, in common with the engine and gears, is firmly bolted 
to the framing of the turret and turns with it. The pinion 
meshes with a large circular rack which is bolted to the deck of 
the ship and lies immediately within the circular steel track 
upon which the turret rotates. The engines are controlled by 
suitable levers and hand-wheels situated within easy reach of 



704 



COMPRESSED AIR AND ITS APPLICATIONS. 




COMPRESSED AIR IN WARFARE, 705 

the officer in the sighting hood, the latter being placed over 
and between the guns. 

The elevation and depression of the gun are effected by 
means of a massive ram, which is hinged to the floor of the 
turret and bears against a shoe on the under-side of the gun 
carriage near the breech of the gun. On each side of the turret 
is a cylinder containing glycerin and water, a portion of which, 
when the gun is to be elevated, is forced by compressed air into 
the ram, the supply being -regulated by valves which are oper- 
ated by means of levers in the sighting station. With his eye 
at the telescope and his hand upon the levers which control the 
air valves of the turning and elevating machinery, the officer 
brings the cross-hairs of the telescope to bear upon the mark, 
and by pressing an electric button hurls a 500-pound steel pro- 
jectile with unerring precision at the hostile ship. 

The recoil of the gun is controlled by two pneumatic cylin- 
ders, 14 inches in diameter and 40 inches in length. The cyl- 
inders below the breech are secured to the gun carriage and the 
pistons to the gun. Before firing, the pressure on the recoil 
side of the pistons is about 500 pounds per square inch. As 
the gun recoils, carrying the pistons with it, this pressure is 
rapidly increased by compression. To reduce the pressure at 
the end of the recoil, a tapered rod is provided, which passes 
through the centre of the piston and allows the air to pass more 
and more freely to the counter side of the piston as the gun 
returns. The residual pressure is utilized to return the gun to 
its firing position. Perhaps there is no part of the many opera- 
tions performed by compressed air on the Terror in which the 
power shows to better advantage — the elasticity of the air pre- 
venting all shock and providing an easy cushion in the recoil 
and counter recoil. 

The last and most important duty performed by the com- 
pressed air is that of steering the ship. The work is performed 
by two long horizontal cylinders which are arranged one on 
each side of the tiller. They are provided with a common 
45 



706 COMPRESSED AIR AND ITS APPLICATIONS. 

piston rod, in the centre of which is a hollow crosshead in 
which the tiller is free to slide as it is swung right or left by 
the movement of the pistons. Compressed air is admitted to 
the outer ends of the cylinders by means of a D valve, the air 
being simultaneously admitted at the back of one piston and 
exhausted from the other, according as the helm is to be put 
over to port or to starboard. Air is also admitted at all times 
at the inner ends of the cylinders, and a pipe connects them, 




-PNEUMATIC STEERING APPARATUS ON THE MONITOR "TERROR." 



so that, as the pistons move, the air may flow freely from the 
inner end of one cylinder to the inner end of the other. In the 
centre of the connecting pipe is a by-pass valve, which is open 
when the tiller is being moved, but closes when it has been 
traversed the desired angle, and holds the air imprisoned in 
the cylinders, thus locking the tiller between two elastic cush- 
ions. The heavy shocks to which the tiller is subject in rough 
weather will thus be received and absorbed by the air, and the 
framing of the ship will be proportionately relieved of the 
strain. 

The general use of compressed air on shipboard may not in 
many cases be as economical as steam, but considering for all 



COMPRESSED AIR IN WARFARE. 707 

emergency cases and where a constant pressure is required at 
points distant from the boilers, there is nothing equal to com- 
pressed air for operating auxiliary fire, bilge, and water service 
pumps; steering engine ; anchor engine ; boat cranes; winches; 
turret-turning engines ; hydraulic cylinders for working guns ; 
ammunition hoists ; ash hydropneumatic hoists ; feed pumps ; 
smoke hose for guns; whistle and siren; to send messages; to 
clear a compartment of water when flooded ; to ventilate and 
to heat and cool the ship. 

Compressed air is better than steam for auxiliary use on 
board ship, for the following reasons: 

The ship is cooler in summer, and men are not debilitated 
by the heat; there are no hot bulkheads all over the ship; the 
auxiliary machinery and pipes last much longer; half the num- 
ber of valves, pipes, etc., are needed; there are no ventilating 
blowers needed to neutralize the heater lines doing the work; 
there is great saving in cost of plants and in the cost of oil ; 
no pipe coverings are needed ; the machines are ready for use 
at once ; there are fewer men on watch in port, and more for 
general work. 



Chapter XXXII. 



COMPRESSED AIR WORK 



COMPRESSED AIR WORK. 

COMPRESSED AIR FOR RAISING WATER. 

The air-lift pump is said to have been invented in the eigh- 
teenth century and in use at Freiberg, Saxony. Siemens in 
England experimented with the air lift in the middle of the 
nineteenth century, and it was patented as an air ejector by 
McKnight in 1 864. The principle of its action became a theme 
with Dr. J. G. Pohle, and to whom two patents were issued,. 
Nos. 338,295 and 347,196, covering the system of elevating 
water by admixture of air under compression suitable for the 
height that the water was to be raised. This system, however, 
required a depth of water in the well more than equal to a 
height to which the water was to be lifted. 

The original Pohle system has been modified and improved 
with a number of patents on special points in the system with 
small gains in efficiency. Dr. Pohle also introduced compound- 
ing or stage-lifting, which has been made available to such an 
extent that it is now possible to lift water to great heights from, 
an ordinary sump in a mine or from ordinary wells. 

We illustrate in Fig. 501 the compressor, receiver, air and! 
lift pipe as usually operated in deep wells, in which the press- 
ure in the air pipe must be greater than the hydrostatic press- 
ure of the water at the bottom of the pipe, and in quantities 
sufficient to make the ascending column of air and water in the 
flow pipe lighter in its total height than the weight of an equal 
column of solid water of the depth of the well from the surface 
of the water to the bottom of the pipe, thus making this prin- 
ciple in pumping water essentially a differential gravity system. 

The air-lift pump proper consists of only two plain open- 
ended pipes, the larger one with an enlarged end piece consti- 



712 



COMPRESSED AIR AND ITS APPLICATIONS. 



tuting the discharge pipe, and the smaller one let into the en- 
larged end piece of the discharge pipe constitutes the air inlet 
pipe, through which the compressed air is conveyed to the 
enlarged end piece to the under side of the water to be raised. 
No valves, buckets, plungers, rods, or other moving parts are 

used within the 
pipes or well. 

I n pumping, 
compressed air is 
forced through the 
air pipe into the 
enlarged end at the bottom of the water pipe; 
thence by the inherent expansive force of the 
compressed air, layers or bubbles of air are 
formed in the water pipe, which lift and dis- 
charge the water layers through the upper end 
of the water discharge pipe. At the beginning 
of the operation the water .surface outside of the 
pipe and the water surface inside of the pipe are 
at the same level ; hence the vertical pressures 
per square inch are equal at the submerged end 
of the pipe, outside and inside. As air is forced 
into the lower end of the water pipe, it forms alternate layers 
with the water, so that the pressure per square inch of the 
column thus made up of air and water, as it rises inside of the 
water pipe, is less than the pressure of water per square inch 
outside of the pipe. 

Owing to this difference of pressure, the water flows contin- 
ually from the outside to within the water pipe by gravity 
force, and its ascent through the pipe is free from shock, jar, 
or noise of any kind. 

These air sections or strata of compressed air form closed 
bodies, which, in their ascent in the act of pumping, permit 
no slipping or back flow of water. As each air stratum pro- 
gresses upward to the spout, it expands on its way in proportion 




Fig. 501. —a 
lift pump 



COMPRESSED AIR WORK. 



713 



as the overlying weight of water is diminished by its discharge, 
so that the air section, which may have been say 50 pounds per 
square inch at first, will be only 1.74 pounds when it underlies 
a water layer of four feet in length at the spout ; until finally 
this air section, when it lifts up and throws out this four feet 
of water, is of the same tension as the normal atmosphere ; 
thus proving that the whole of its energy was used in work, 
and that this pump is a perfect expansion engine. 

As the weight of the water outside of the discharge pipe 
(the head) is greater per square inch than the aggregate water 




FIG. 502.— THE CLAYTON DUPLEX AIR COMPRESSOR AND AIR LIFT PUMPING APPARATUS. 



sections within the pipe when in operation, it follows that the 
energy due to this greater weight is utilized in overcoming the 
resistance of entry into the pipe, and all the friction within it. 

The Pohle " air-lift " pump has been found to give above 
80 per cent of efficiency from the air receiver in water pipes 
of large diameter, and, as a rule, above 70 per cent in small- 
sized pipes. It retains this efficiency without repairs, or until 
the pipes rust through, whereas ordinary bucket-and-plunger 
pumps gradually lose efficiency from the first stroke they make, 
and lose it rapidly if the water contains sand or is acid in char- 
acter. 



7 H COMPRESSED AIR AND ITS APPLICATIONS. 

The secret of the air-lift pump action is in the high velocity 
with which the air and water are discharged through the educ- 
tion pipe. Without this high velocity there would be no piston- 
like sections except perhaps in a small glass tube model where 
capillary attraction takes the place of velocity. 

As the pump has no valves, no standing water remains in 
the pump column after the operation of pumping; it recedes 
into the well, and there is none left to freeze in cold weather. 
The capacity of the pump is unlimited, and, with the proper 
proportions of air to the water, will work efficiently in pipes 
several feet in diameter. Estimates have been made which 
indicate that a 30-inch pipe will deliver 16,660 gallons per min- 
ute, equal to 1,000,000 gallons per hour. 

As sand, silt, gravel, and bowlders in water form no obsta- 
cles to interfere with the action of the pump, its adaptability 
for dredging is suggested as well as its utility for pumping 
sewage. Experience has proved that, by the use of this con- 
stant upward flow of water, artesian wells have been freed from 
their accumulated sedimentary deposits, as well as that lodged 
in the fissures and crevices of their wall rock, and have been 
thus made to yield greater quantities of water than they ever 
did before. For chemical uses, and for the liquids of the arts, 
there is no superior method than the "air lift." It is used suc- 
cessfully for raising sulphuric acid of high specific gravities, 
and is well adapted for ore-leaching works, vinegar works, 
sugar refineries, dye works, paper-pulp works, etc. 

As an irrigating pump for raising subterranean water in the 
arid regions of the West, its field of usefulness is very promis- 
ing, for with one air-compressing plant at a central station, a 
number of wells, widely separated from one another, may be 
simultaneously pumped by branches of air-conveying pipes, 
taken from a main air pipe from the air compressor; for com- 
pressed air may be conveyed for miles without material loss of 
power. 

It often happens that a single well does not yield the quan- 



COMPRESSED AIR WORK. 715 

tity of water desired, but that a number of wells would give the 
satisfactory result. By the old-fashioned deep-Avell pump, each 
well would require a separate "steam head," separate sets of 
rods, and the other paraphernalia, which, with the condensa- 
tion of the steam, when conveyed to the several steam heads, 
would be very costly in the first outlay, and very wasteful of 
power in its- maintenance, to say nothing of loss of time in re- 
pairs. By the Pohle process, but one air-compressing plant is 
required, and this may be placed in the engine room or the 
boiler house, directly under the eyes of the engineer, from 
whence the air may be conveyed to the several wells, all of 
which may be pumped simultaneously and economically. 

In Fig. 501 is illustrated the air-lift system of the Ingersoll- 
Sergeant Drill Company, New York City, with which company 
Dr. Pohle was associated in the last years of his life. 

In the early trials for efficiency of the air lift some curious 
comparisons were brought out relative to the ratio of the lift to 
the depth of submersion and the relative air pressure due to 
submersion. 

Thus with 16 pounds air pressure with 41 feet water lift and 
10 feet submergence, 68 cubic feet of free air per minute lifted 
•| cubic foot of water 41 feet high, giving a computed efficiency 
of 3^- per cent of the steam power. The efficiency was found 
to decrease with the increase of air pressure above what was 
necessary to do the work; for instance, with an equal sub- 
mergence and lift of 26 feet and an air pressure of 20 pounds, 
64 cubic feet of free air pumpeJ 14 cubic feet of water 26 feet 
high per minute, showing an efficiency of 19 per cent of the 
steam power in the compressor. When the air pressure was 
reduced to 12^ pounds, using 26 cubic feet of free air per min- 
ute and pumping 8^- cubic feet of water 26 feet high per minute, 
the efficiency was raised to 42 per cent. It was found on trials 
that on a deeper submergence of 1 to 1.6 the efficiency rose to 
53 per cent, and in all trials was greatest at the lowest pressure 
that the lift could be operated. It was found on a general aver- 



yi6 COMPRESSED AIR AND ITS APPLICATIONS. 

age that the efficiencies that may be expected from the best 
conditions for air compression may be stated as follows : 

^ = .5 efficiency 50 per cent. 

Submergence 

1.0 " 40 " 

1.5 " 30 

2.0 " 25 " 

Mathematicians have formulated some complicated equations 
in relation to the action of the air in the ascending column of 
water ; but as the air bubbles vary in size according to the form 
of the injecting nozzle, and as their coalescence and expansion 
produce so many variable factors, reliable results can be ob- 
tained only from actual tests, and even these are merely ap- 
proximate. 

In a test of the Pohle air-lift made at De Kalb, 111., the air 
pipe was placed inside of the well pipe with a water lift of 133 
feet, and the submerged nozzle 123 feet below the surface, a 
nearly equal ratio. The well pipe was 6 inches diameter, air 
pipe 2-1- inches, thus adding about 50 per cent to the friction of 
the ascending water and giving to the whole length of 256 feet 
an irregular annular space for the passage of the water and air. 
With the expenditure of 42.7 horse-power indicated, there was 
raised 207 gallons of water 133 feet, with a volume of 310 cubic 
feet of free air per minute. The efficiency was found to be 
\y\ per cent. This shows very plainly that the friction of an 
internal air pipe causes a loss of efficiency. 

A series of trials with a gang-well system on the Pohle plan 
was made at Rockville, 111. In casings of 6\ inches diameter 
inserted in four wells, 260 feet below the overflow, and air 
pipes i-|- inches diameter, let down 250 feet, all in 8-inch drilled 
wells. After several trials with return bends and small nozzles 
at the bottom of the air pipes with unsatisfactory results as to 
water flow, the bottom of the air pipe was closed and the sides 
slotted for 20 inches up from the bottom, giving a full and free 
opening for the air without any obstruction to the upfiow of the 



COMPRESSED AIR WORK. 717 

water. In this manner the service was raised from 1,000 gal- 
lons to 1,400 gallons per minute, but still showing an efficiency 
of only 24 per cent. 

Much doubt has existed from the early years of the air-lift 
system as to the possibilities in regard to conveying the water 
to a distance or direct to an elevation at a distance from the 
well. Lately there has been constructed at Point Pleasant, W. 
Va., on the bank of the Ohio River, a water-works employing 
the air-lift system to obtain water filtered into the gravelly soil 
beneath the river. The compressor was located in a power 



Fig. 503.— profile of the point pleasant water-works. 

house 500 feet distant from the location of the wells on the river 
bank. The receiving basin is situated at the top of the river 
bank, 67 feet above the top of the well pipes and 400 feet from 
the low-water bank of the river. In Fig. 503 is shown a profile 
of the situation. Well casings 10 inches in diameter were 
driven to the rock about 40 feet in depth. 

After the 10-inch casings were in place 10-inch holes were 
drilled in the underlying rock 1 16 feet deep, and cased 8 inches 
inside diameter from bottom to top. This casing was also per- 
forated similarly to the outer one, only the holes were larger — 
^ inch. The space between the two casings was tightly calked 
at the top to prevent water entering the wells at this point. 



71 8 COMPRESSED AIR AND ITS APPLICATIONS. 

Four-inch discharge pipes and i|-inch air pipes were properly 
fitted and suspended in each of the wells, with their extremities 
1 10 feet below the top of the 8-inch casing. 

Both pipes were suspended from a water-tight cap, resting 
on the top of the 8-inch casing. It will be observed that no 
water can enter these wells except through the perforations in 
the casings, which are 10 feet to 20 feet below the flowing 
water in the river. None can enter at the bottom. It was the 
desire to allow the river water to enter the wells only through 
the perforations after having passed through the sand strata 
mentioned, which would serve as a filter ; which has proved that, 
however muddy the river may be, the water taken from the 
wells is bright and sparkling at all times. 

Just when the wells were completed and the pipes in place 
and extending up the sloping river bank a short distance, the 
river rose over the wells. For two months the wells stood 
unused. In the mean time the reservoir, receiving basin, and 
power house were completed, and the work advanced as fast as 
possible. Just as soon as the air compressor was in place the 
air pipes were connected up and the wells tested before the 
discharges were extended to the receiving basin. One well was 
found with a deposit of sand in the bottom reaching 5 feet above 
the foot of the discharge pipe. Several unsuccessful efforts 
were made to force air into this well. The river having re- 
ceded, the air pipe was disconnected at the top of the well and 
a -f-inch gas pipe coupled and lowered. It stopped 5 feet from 
the bottom. It was churned a few minutes and soon went 
down the remaining 5 feet. Again the air pipe was coupled 
and the air pressure increased to 90 pounds per square inch. 
The effect was almost startling, but gratifying. The obstruc- 
tion was cleared out very quickly. No other system of pump- 
ing could possibly have accomplished the clearing out of this 
well of the sand deposit. 

The discharge and air pipes to each well are independent. 
That is, each well has a separate discharge to the receiving 



COMPRESSED AIR WORK. 719 

basin and a separate air pipe from the receiver. These are 
carefully graded and are not exposed at any point except where 
the discharges pass through the top of the walls of the receiv- 
ing basin, and have open discharge. 

The working pressure is from 45 to 50 pounds, varying with 
different river levels. 

The discharge of water is not constant, however, but irreg- 
ular or intermittent, as though the air and water formed alter- 
nate strata or volumes within the discharge pipes. It varies 
with the depth of water in the river, ranging from 1 volume 
of water to 8 volumes of free air, to 1 to 6. As the river is 
constantly rising and falling and is frequently 25 to 40 feet 
deep over the wells, the pressure on the sand surrounding the 
wells is constantly changing and affects the capacity of them 
as well as the necessary air pressure to pump them. 

The reservoir is situated about \\ miles distant and at 225 
feet elevation. Water is taken from the receiving basin by 
belt-driven triplex outside-packed plunger pumps, 9 inches 
diameter by 12-inch stroke, operated at 37 revolutions per 
minute, delivering about 22,000 gallons per hour. 

As there is no demand in the town for electric current dur- 
ing the day, the works are operated at night only. Usually the 
air compressor is operated one night, and the following night 
the forcing pumps. The water received the previous night in 
the settling or receiving basin has about twelve hours to be- 
come cleared of any sand brought with it from the wells before 
going to the reservoir. This basin has a capacity of about 
225,000 gallons; the reservoir about three times this quantity. 
The construction of the receiving basin is the same as the reser- 
voir. The engine has ample power to operate all the machin- 
ery at the same time. Two men only are required to attend 
the combined plant. In addition to the public and private 
consumption of water, two busy railroads are consumers. All 
customers are served by meter, and therefore there is practi- 
cally no waste. 



720 COMPRESSED AIR AND ITS APPLICATIONS. 

There can be no doubt that water taken by air in this man- 
ner is purified to some extent, the admixture of air serving to 
oxidize and destroy organic matter. Samples of the water 
taken are bright and sparkling, have no odor, and remain ap- 
parently unchanged. There probably is not another town of 
5,000 inhabitants in the country that has a better or more com- 
plete combined water and light works. Certainly there is not 
another town of any size on the banks of the Ohio River from 
Pittsburg to Cairo that has better water, if as good. 

The works have been in constant operation since built. 

What has been accomplished at Point Pleasant can be done 
at hundreds of other small towns similarly situated where there 
is no water-works. Here it has been demonstrated that bright, 
sparkling water can be obtained from a muddy, filthy stream 
without the use of chemicals or mechanical filters. 

Just use the filter nature has so abundantly supplied at the 
bottom of such streams, and by proper arrangement of the 
pumping system combined with an electric-lighting system, 
thus economizing the operating expenses to a minimum, estab- 
lish first-class water and electric service on a paying basis when 
neither separately would pay operating expenses. 

The air-lift system is undoubtedly the simplest as well as 
the best of all known methods of serving such towns with good 
water. Nor is the system less applicable to larger towns, as 
well as to factory and domestic supply. 

Artesian wells, or wells supplied from land sources, gener- 
ally yield hard water or water highly charged with mineral 
salts. The water at Point Pleasant is soft, pleasant, and whole- 
some. The railway companies using it speak very highly of 
it. It is simply Ohio River water freed of filth and all objec- 
tionable matter that render it so disgusting at many towns 
along the stream. 



COMPRESSED AIR WORK. 



72 1 



: ^S 



; ^"'l/4| 

1 J 



THE COMPOUND AIR LIFT. 

The idea of compounding the air lift was first proposed by 
Dr. Pohle, and has since come into use for shallow sumps. Fig. 
504 represents the conditions of a sump of about one-quarter of 
the total lift in depth, in which an auxil- 
iary pipe is introduced to receive the 
water at about twice the depth of the 
sump to act as a pump well for a higher 
lift. By this method the inconvenience 
and cost of a deep shaft or boring may be 
avoided and the compound system quickly 
applied in emergencies. 

As yet we have no data as to its effi- 
ciency for permanent use, but there is no 
doubt that economy due to decreased air 
pressure will be found to warrant its 
adoption in mine and drainage work. 

MULTIPLE STAGE AIR-LIFT PUMPING. 

In Fig. 505 we illustrate the possibili- 
ties in the work of compressed air in 
pumping water to great heights from 
shallow sumps by the Pohle air-lift sys- 
tem . In order to show the detail of opera- 
tions the illustration is spread out. In 
practice the several wells may be bunched together to occupy 
the smallest space in a mine shaft. It will be readily perceived 
that but one air pressure is needed, no more than sufficient to 
operate the highest lift in the multiple-stage system. The lesser 
lifts may be regulated by valves in the air branches to exactly 
meet the volume and pressure required for the lower lifts. Its 
air economy may balance the cost of a deep sump, but its effi- 
ciency is yet to be tested. 
46 




-DUPLEX AIR LIFT. 



7 2. 



COMPRESSED AIR AND ITS APPLICATIONS. 




Fig. 505.— multiple stage air lift 



THE AIR-LIFT PUMPING SYSTEM OF THE 

PNEUMATIC ENGINEERING COMPANY, 

NEW YORK CITY. 

The special feature of the air-lift pump- 
ing system of this company is due to the 
patents of Mr. S. W. Titus, which claim 
an air tube within the well tube, closed at 
the lower end and perforated with lateral 
orifices at different points in its height 
with a series of cylindrical valves corre- 
sponding with the orifices, differentially, 
and attached to a central stem projecting 
above the top of the air pipe and terminat- 
ing in a screw, yoke, and valve wheel. 
The relative positions of the orifices and 
valves are so arranged that they can be 
opened successively from the top downward 
to control the air pressure required for the 
varying heights of the water in the well, 
which in most wells varies greatly with the 
quantity pumped. By this device, which is 
operated by the valve wheel at the top 
of the well pipe, the best point of sub- 
mersion of the air pipe for the most eco- 
nomical use of air required for the vary- 
ing height of the water level in the 
well and the height to 
which the water is to 
be pumped, is obtained. 
The section to the left 
in Fig. 506 shows a dou- 
ble-tube well ; the sec- 
tions are self-explana- 
tory. 



COMPRESSED AIR WORK 




FIG. 506— AIR-LIFT PUMP OF THE PNEUMATIC ENGINEERING COMPANY. 




Fig. 507.— a line of wells operated by compressed aik. 



724 



COMPRESSED AIR AND ITS APPLICATIONS. 



Fig. 507 is a scenic view of a system of air-lift gang wells 
discharging into the funnels of an underground conduit hav- 
ing a gravity flow to a basin from which the water may be 
pumped to a high reservoir. 

A direct system of pumping water by compressed air under 
the patents of Prof. E. G. Harris is operated by this company. 

The name "direct air- 
pressure pump " is applied 
to that class of pumps in 
which the liquid is taken 
into an air-tight vessel and 
then driven out by the ap- 
plication of compressed air 
directly to the surface of 
the liquid. For instance, 
if the vessel B (Fig. 508) 
contains water, and air be 
forced in through the pipe 
C, the water will be driven 
out through the pipe A. 
The apparent simplicity of 
this operation, and the ab- 
sence of costly cylinders, 
pistons, rods, valves, etc., 
have made it a popular 
means of water supply with various modifications. This system 
is not a new one, having been patented by Upham in 1809, and 
the system in its duplex form was patented in England in 1865. 
The apparent difficulty in the use of this system lies in the 
loss of power when the compressed air in B, after driving the 
water out of the vessel, is allowed to escape into the atmos- 
phere, thus losing all the power that was required to compress 
the air. The percentage of this loss increases with the head 
against which the water is pumped, and is about 50 per cent 
when pumping to a height of 100 feet. 




-DIRECT-PRESSURE SYSTEM. 



COMPRESSED AIR WORK. 



725 




In the following system, the above difficulties are overcome 
to a degree that cannot be surpassed ; for in it there are no 
floats and the air is not allowed to escape, being used over and 
over so that none of the work done on it is directly lost. 

Fig. 509 
shows how the 
above condi- 
tions are at- 

teis " tained. Sup- 

=2 

pose the compressor to be in operation 

with switch set as in the figure ; the air will 
be drawn out of the right-hand tank and forced 
into the left-hand tank; and in so doing will 
draw water into the former and force it out of 
the latter. The charge of air in the system 
is so adjusted that when one is emptied the 
other is just filled. At that moment the switch 
will reverse the pipe conditions so that action 
in the tanks will be reversed. 

The automatic control of 
the action of the pump is made 
by an air switch at the com- 
pressor, which is thrown by 
the differential pressure in the 
air pipes. The change in the 
pressure of these pipes alter- 
nating between the hydrostatic 
pressure in the air force pipe 
and the absolute pressure in the air suction pipe is equal to the 
head of water in the tank above the water level in the well. 
At the moment of the greatest difference in pressure in the air 
pipes, the automatic switch reverses the connections, and the 
compressor draws the air from the empty chamber and forces 
it into the full chamber. The compression and expansion 
nearly balance each other, and there is but little loss in power. 



Pump 7aa/ks 



WATER SUPPLY 



Fig. 509.— duplex automatic water lift 



Automatic^ 
Air <- 



^U 



726 COMPRESSED AIR AND ITS APPLICATIONS. 

The same system, as shown in Fig. 510, may be operated as 
a two-stage or compound water lift by placing one of the cham- 
bers in the well or sump and discharging its water into a sump 
or open tank at a higher level. They may be operated alter- 
„ ., , nately as before, and thus be made 

Switch <— J ' 

)f ; ^ f~jj F~~^;_ to raise one-half the volume of 
iLh N water to double the height, or 

J) Compressor 

raise one-half the volume to the 
same height with one-half the air pressure. 

The size of air pipes in this system re- 
quires a somewhat complex adjustment in re- 
lation to the size of the water chambers and 
the height of the water lift, as well as the 
distance of the compressor from the chambers, 
for the best economy ; the work of compression and 
expansion in the air pipes being an absolute loss 
subject to economical adjustment for least friction, 
j while the compression and expansion in the displace- 

fig. 510.-TW0- ment chambers are a necessary loss to meet the 
pump!' AIR "" FT hydrostatic conditions of the height to which 
the water is raised. 
Its efficiency is due to the well-balanced condition of the 
pumping plant, including the compressor, sizes and length of 
air and water pipes, that the friction may be a minimum for the 
quantity of water to be pumped. Under the best conditions, 
an efficiency of 65 per cent of the indicated work of the com- 
pressor may be expected at 75 pounds air pressure, pumping 
water to a possible height due to that pressure, and varies in- 
versely with the height and pressure. 

The principle of the direct air-lift pump with discharge of 
air at each stroke is illustrated in Fig. 512 by one of the earlier 
methods of operating the air valve by a float, which was placed 
on the outside of the chamber and connected with the top and 
bottom of the chamber by a flexible tube; so that the float, 
alternately filled with water or air by hydrostatic equilibrium 



H^i 



COMPRESSED AIR WORK. 



727 



through the flexible tube connection, was raised at the moment 
of full discharge of water from the chamber, throwing, the air 




;he automatic switch of the Harris system. 



valve open to the exhaust and closing the air inlet. The water 
rising in the chamber filled the float at its upper position, when 
it fell by its weight, fully opening the inlet air valve and clos- 
ing the exhaust. A flap valve on 
the bottom of the chamber admit- 
ted the water by gravity. This 
system has been modified in vari- 
ous ways by rods directly connected 
to the air valve and a sliding float 
within the chamber, one form of 
which is illustrated in Fig. 513, in 
the Halsey pneumatic pump, which 
consists of a tank submerged in 
the water or other liquid to be 




FIG. 512.— FLOAT-GOVERNED AIR-LIFT 
' PUMP. 



728 



COMPRESSED AIR AND ITS APPLICATIONS. 



pumped. From the air valve contained in the top casting a 
rod descends through the tank, having a float upon it, this float 
being an. inverted bucket of sheet metal. The water flows into 
the tank when the air exhaust is open, the inverted bucket rid- 
ing on top of the water; and when full the bucket engages with 



■BEII 




Fig. 513.— the halsey direct-air-pressure pump. 



a collar on the top of the rod lifting the same, opening the air 
valve and closing the exhaust. The air is thus admitted di- 
rectly to the surface of the water and forces it out. As the 
water level descends the bucket at the lower end becomes un- 
covered; its weight pulls down the rod and reverses the valve, 
thereby discharging the air, when the operation is repeated. 
We should say that the rod described also operates a supple- 



COMPRESSED AIR WORK. 



729 



mentary valve which turns the air into one or the other end of 
the main valve-chest precisely like a common steam pump. It 
is plain that the machine is entirely automatic and extremely 
simple, and adapted to a very wide range of uses. It is part of 
the Pneumatic Engineering Company's pumping system. 

In the Clayton patent lately issued, a sealed float rises and 
falls on a rod with stops to operate the 
air valve. 

A combination of the direct-acting 
tank system and the Pohle expansion air 
lift has been devised by Mr. Wheeler, by 
which the high-lift system maybe utilized 
from a shallow sump by raising the water 
about one-half the height by direct press- 
ure, then injecting air under the water 
column from the same air pipe used for 
the direct lift, and thus doubling its ele- 
vation. In Fig. 514 is shown a sec- 
tional elevation of this system, in which 
A is the direct pressure or displacement 
chamber, from which the water is raised 
to a height at C ; air is injected at B, and 
by its lifting and expanding action com- 
pletes the lift; the pressure in the cham- 
ber A being equivalent to the deep immer- 
sion required in the Pohle system. This system, as shown in 
the figure, is alternating, and evidently could not run constantly 
with one chamber; but by making a double-chambered direct 
lift as in Fig. 518, and connecting the air pipe to the water 
column direct from the pressure side of the air compressor, and 
using the air switch only on the direct-lift pipes, a continuous 
flow would be obtained. 

The efficiency of the Wheeler pneumatic pump just de- 
scribed compares very favorably with any of the other methods of 
pumping by air pressure. In a series of tests made by Mr. H. 




.—COMBINED AIR- 
LIFT PUMP. 



73Q 



COMPRESSED AIR AND ITS APPLICATIONS. 



C. Behr, published in Compressed Air, the computed effi- 
ciencies under varying conditions of air pressure of from 19 to 
41 pounds per square inch for a lift of 105 feet from a shallow 
sump, as shown in Fig. 5 14, were from 24 to 48 per cent of the 
least work needed from the compressor, or from 17 to 30 per 
cent including the efficiency of the compressor. 



COMPRESSED-AIR PUMPS OF THE MERRILL MANUFACTURING 
COMPANY, NEW YORK CITY. 



We illustrate in the following figures the automatic com- 
pressed-air system of the above-named company, who are operat- 
ing under the patents of Mr. F. H. Merrill. By this system air 
may be compressed at any available distance from a well or 
water supply, and perform its whole duty, save friction, in 

pumping water to any re- 
quired height or into hori- 
zontal mains to distant res- 
ervoirs. 

The apparatus consists 
of one or two water cham- 
bers, adapted to be sub- 
merged at the source of 
water supply, and an auto- 
matic air valve located 
above the water and con- 
nected with the chambers 
by one or two air pipes. 
The automatic air valve di- 
rects compressed air to and 
from the water chambers, 
from which the water is al- 
ternately discharged by the direct action or displacement of 
the compressed air, without the intervention of pistons or 
other complicated mechanism. 




Fig. 515.— single-acting pump. 



COMPRESSED AIR WORK. 



731 




— 



Fig. 516.— automatic air-valve head. 



By the duplex arrangement of chambers a perfectly steady 
discharge is obtained. 

The automatic air valve (Fig. 516) is by far the most impor- 
tant part of the apparatus. This 
device is a remarkably simple and 
ingenious mechanism, self-con- 
tained and certain in its action. 
It is actuated solely by compressed 
air applied on differential surfaces, 
and is entirely independent of the 
water chambers. The valve head 
contains a double-disc differential 
air valve, which is operated in one 
direction by compressed air through 
a small valve port opened by a water float in the under sec- 
tion .of the valve head, and in the opposite direction by a 
spring. The water enters by a pipe connection with the main 
discharge pipe and is released by the air when the water in 
the pump chamber falls to the discharge valve by the uncover- 
ing of a supplementary pipe 
connected with the float 
chamber. The throw of the 
differential valve operates a 
piston valve to change the 
flow of compressed air alter- 
nately from one chamber to 
the other, and also alter- 
nates the exhaust. 

The single chambers are 
made for capacities of 25 
and 50 gallons per minute. 

In Fig. 517 is shown the 
internal construction of the 
water chamber with the inlet 
and discharge water valves. 





FIG. 517.--SECTION, WATER VALVES. 



732 



COMPRESSED AIR AND ITS APPLICATIONS. 



In Fig. 518 is represented the larger size of a duplex direct- 
acting air pump having a capacity of from 200 to 350 gallons 
per minute. 

With this class of water lifts it is not necessary to place the 
operating valve mechanism near the water chambers as repre- 




FIG. 518. -THE DOUBLE-CHAMBERED PUMP. 



sented in the figures, but at any convenient location at the top 
of the well where it can be easily inspected; then there will 
not be less efficiency of the pump than is 
due to the volume of the air in the connect- 
ing pipes, between the valve and chamber. 
A differential piston air-lift pump (Fig. 
519) is made by this company, adapted for 
light duty and domestic service, and is de- 
signed for pumping from driven wells or 
any place where a displacement pump cham- 
ber cannot be inserted or submerged. 

It consists of two brass differential cyl- 

FlG. 519 — DIFFF.RENTIAL . , .. . : 

piston pump. mders, having connected pliable packed 




COMPRESSED AIR WORK. 



733 



differential pistons, and an air-pressure controlling valve in 
the head of the larger cylinder, actuated by the pistons at the 
extreme end of their strokes. 

This little pump will fill the requirements of many light 
duty cases, using compressed air furnished by an air compres- 
sor located any distance away, driven 
by any available power — belt, steam, 
electricity, gas, or oil. It is suitable for 
any suction up to 15 feet and for 50-feet 
lift. 

In Fig. 520 is shown the combination 
inductor and displacement pump, for 
use in bored wells, in which the induced 
lift on the principle of the Pohle air lift 
raises the water to a displacement cham- 
ber in a pit at the surface, from which 
it is raised to the required height by 
direct air pressure. 

In Fig. 521 is shown a section of a 
gang system of air-lift wells with cen- 
tral displacement pump. 

In Fig. 522 is shown a Merrill water- 
pumping system for service where it is necessary that the valve 
mechanism or working parts be placed some distance from and 
above the water chambers, as in the case of rivers where the rise 
and fall of water are great, and where it is desired to have the 
controlling valve above high water, and accessible at all times. 

By this system of arranging the location of the air valve 
above and at a distance from the location of the well or intake, 
and thus facilitating a pure water supply for public and private 
use by locating the wells in the filter sands of streams and 
water-courses with the air valves on the bank and an air-com- 
pressing station at any convenient distance, a valuable water- 
supply service may be made available at all times and under 
any condition of flood that would otherwise derange the old 




-COMBI.\'ATIO> 



34 



COMPRESSED AIR AND ITS APPLICATIONS. 



systems of water supply from rivers. The only precaution 
necessary would be to build the well curb above the flood line, 
or cover the well with sand and carry the exhaust pipe up the 
bank, or to a safe place out of flood-water range. In this man- 
ner the neglected and scanty water supply of towns and fac- 
tories may be reinforced with the pure and filtered element so 
essential to life and prosperity. 

Air pressure is used for elevating milk in dairies and for 
aerating milk. For elevating, the milk is poured into large 




Fig. 521. -the gang system of bored or driven wells. 
In combination with the direct air-pressure lift. By this method a settling basin will gather the 
sand from the bored wells, and the direct displacement pump will be free to pump clear water. 



cans, the top closed and connected with an air pump. A pipe 
from the bottom of the can conveys the milk under air pressure 
to any required height or distance. 

Color liquids in dye houses which are destructive to pumps, 
or are injured by contact with the metals of pumps, are elevated 
or discharged at various points through pipes suitable for the 
coloring fluids, by direct air pressure. 



COMPRESSED AIR WORK. 



735 



In chemical works the same system of transfer of acids is 
used. 

The manufacture of sulphuric acid is a compressed-air proc- 
ess in which the large condensing chambers are dispensed with 
and the process is made more direct and compact. The sulphur 
is burned under air pressure in an air-tight furnace, and by the 



< 4-5 H 




FIG. 522.— THE MERRILL PNEUMATIC PUMP. 

Direct acting, with elevated air valves. 



same pressure the products of combustion are forced through 
pipes beneath water in a closed tank, rising in bubbles, and so 
on through a series of tanks, until the entire acid product is 
absorbed. 



ECONOMY OF COMPRESSED AIR IN PUMPING. 

Fig. 523 represents what has been termed the endless chain 
of pneumatic power, by which a volume of air is compressed, 
transmitted to a pump or motor, does work, is exhausted into 
a return pipe, and retransmitted to a low-pressure receiver at a 



736 



COMPRESSED AIR AND ITS APPLICATIONS. 



low temperature, and again compressed to the proper working 
pressure for another round in this cycle of air work. It has 
been in use in California for several years with success for 
pumping and drilling, and is known there as the " Cummings 
process " or system. 

The economy of this system is most apparent in eliminating 
frost at the exhaust and the conservation of heat. The mois- 




FlG. 523. — THE ENDLESS CHAIN IN COMPRESSED-AIR WORK. 



ture in the air is soon condensed and deposited in the low-press- 
ure cold-air receiver, when the system becomes a dry-air one, 
and may be operated as a dense-air system by which the adia- 
batic losses are lessened by operating on the greater curve of 
heat expansion and contraction due to higher pressures as well 
as the less differentiation of volumes at the higher pressures. 
This singular property of compressed air is graphically illus- 
trated in the diagram (Fig. 45). It is also in use in the Allan 
dense-air refrigerating machine. 

The economies of this system, due to working pumps and 



COMPRESSED AIR WORK. 737 

drills or motors that carry full pressure nearly to the full stroke, 
have been worked out by Mr. A. E. Shodzko, who has found 
an efficiency of .69 with working pressures of 200 and 100 
pounds in the two pipes, as against .33 in the single-pipe sys- 
tem, as ordinarily used, as between the compressor and motor. 
With reheating the efficiency is increased in this system to a 
possible 85 per cent. In ordinary pressures used in mining 
machinery, say up to 90 pounds, and exhausting into the return 
pipe at 30 pounds pressure, the continued operation will work 
under a temperature cycle of 200 F., while in the single-pipe 
system with open exhaust the working cycle is about 300 F. 
under the same operative pressure. 

The claim for efficiency and practicability for this system 
seems to have been criticised by assuming that the motor, 
pump, or drill must be operated at full pressure for the full 
stroke; but this claim is not reasonable, for the possibilities of 
expansion between the initial pressure in the flow pipe and the 
pressure in the return pipe only involves the air friction in the 
two pipes, leaving a considerable margin for expansion econ- 
omy in motors ; but this principle cannot be applied to rock drills 
and hoisting engines further than their fixed cut-off. 

COMPRESSED AIR FOR LIFTING SEWAGE. 

The Shone system as used in England is illustrated in a ver- 
tical view of the air lift in Fig. 524 and a plan in Fig. 525, which 
represents the sewerage system in the city of Norwich, Eng- 
land. The old works were subject to floods in the lower part of 
the city ; by the apparatus shown in the illustration the old sewers 
were intercepted at five points near the river, and water lifts by 
direct air pressure were located to lift the sewage from 15 to 2 1 
feet in different localities to a main outfall sewer that discharged 
at a distant pumping station, from which it is pumped to a 
sewage farm. A pair of turbine wheels at the dam above the 
town operate the compressors at 18 pounds pressure, which dis- 
47 



738 



COMPRESSED AIR AND ITS APPLICATIONS. 



charge 650 cubic feet free air per minute into two large re- 
ceivers, from which the compressed air is distributed through 




m 



j_Li^^frAy4ai!^S3Jd4feyy*. j -w 




Fig. 524.— elevation of sewage lift. 



underground mains to the different lift stations. Each station 
is provided with two air-lift chambers with floats and trip valves 
or rods to operate the air valves. The ejector chambers vary 




Plan 
Fig. 525.— plan df sewage lift. 



COMPRESSED AIR FOR PURIFYING WATER. 739 

in size at the different stations to meet the variation in sewage 
flow from the districts converging at each station, ranging in 
cubic contents from 300 to 2,000 gallons. 

The automatic pneumatic cesspool drainage is extensively 
in use in the United States. Its convenience and value from a 
sanitary point of view cannot be overrated. A simple form of 
this device is in operation at La Crosse, Wis., to clear the pits 
of a round-house; consisting of a large tank in a catch-basin, 
in which a float slides upon a rod between stops that opens a 
three-way valve in an air-pressure pipe which discharges the 
water to a higher level sewer, the water flowing into the tank 
by gravity through a flap valve on the release of the air press- 
ure through the action of the float and valve. 

AERATION OF WATER BY COMPRESSED AIR. 

It is well known now, among hydraulic engineers, that an 
ample aeration of water in tanks and reservoirs will prevent 
stagnation, check the growth of algae, remove the disagreeable 
odor from decomposing vegetable matter, and deposit the salts 
of iron that sometimes pervade waters from iron soils or that 
have traversed long lines of iron pipe. Fig. 526 represents the 
pipe plan for aerating a tank 62 feet in diameter, 59 feet high, 
holding 1,300,000 gallons, at Brockton, Mass. 

In the bottom of the tank are three 2 -inch galvanized iron 
pipes which radiate from a point near the side as shown. The 
centre arm is 56 feet long, and the two side arms 47 feet. 
Spreading out from these pipes are thirty-nine brass tubes one- 
quarter inch in diameter, except five long branches from the cen- 
tre arm, which are three-eighths inch in size. 

The small pipes are perforated at distances of 3 feet with 
^--inch holes, and are supported on iron chairs which hold them 
clear of the bottom. The 2-inch pipes are carried through the 
supply pipe from the pump, and furnished with valves to con- 
trol the flow of air. They are finally connected with a 2-|--inch 



74Q 



COMPRESSED AIR AND ITS APPLICATIONS. 



pipe from the pumping station, which is provided with a check 
valve to prevent water from going to the pump. The air is 
supplied by a y\ x 9 x 9 inch Chiton duplex compressor, fur- 
nishing 172,000 cubic feet of air in twenty-four hours. The air 
is forced directly into the tank, no receiver being used. By 
this means the water is thoroughly agitated and aerated, doing 
away with its former odors and taste. 

Another method of aeration of water is by pumping air di- 
rectly into the main between the intake and the reservoir, and 

into the delivery main from 
a reservoir. 

In another case, in order 
to improve a supply drawn 
from a lake in which algae 
had given some trouble, a 
1 2 -inch pipe was laid from 
the gate house at the lake 
for a distance of 350 feet to 
within 50 feet of the lowest 
part of the main. At this 
point a small Clayton com- 
pressor, driven by a 10-inch 
double-discharge turbine, was set up. This plant required 
259,000 gallons of water in twenty-four hours to force 82,250 
gallons of air into the 200,000 gallons of water supplied to the 
town from the lake. When the water was turned on to the 
wheel, the air was forced into the main against the flow in the 
pipe and rose toward the lake, coming up through the gate 
house in great volumes and agitating the water with consider- 
able violence, so that it immediately lost its taste and odor. 
The pressure of the air as delivered from the compressor was 
20 pounds per square inch. In this connection, attention is 
called to the aerating plant at Charleston, S. C, where equal 
satisfaction has followed the adoption of this method of puri- 
fication. Every practical superintendent and engineer who has 




Fig. 526.— water-tank aeration. 



COMPRESSED AIR FOR PURIFYING WATER. 74 1 

had any extended experience with aeration seems to favor it, 
as far as we have been able to learn. As the subject now stands, 
it is pretty generally admitted that aeration will prevent stag- 
nation, check the growth of algas, remove disagreeable gases, 
and deposit the salts of iron that sometimes occur in a ground 
water, although it has yet to be proved that it will hasten the 
oxidation of organic matter. 

Water in its natural state is never found chemically pure ; 
matter more or less foreign is identified with it and detected 
under the test of the chemist. Nevertheless, waters thus found 
are fit for human consumption, and, taken from nature's labora- 
tory, are pure enough for general use. 

The methods adopted for purifying water are oxidation or 
aeration and filtration. Nature herself practises and carries 
on successfully the process of purification. When her adminis- 
tration is interfered with by man's construction of dams and 
reservoirs to confine her waters, it then becomes necessary for 
him by mechanical means to imitate her example. In this 
attempt he must recognize her laws. Oxidation or aeration is 
one of nature's processes carried on successfully for the purifi- 
cation of water. The oxygen is dissolved in the water, coming 
in contact with whatever organic matter may be associated with 
the water, changing it into nitrites and carbonic acid. The 
greater the agitation of the waters, the greater the beneficial 
changes thus wrought. 

Cascades, fountains, the introduction of air to conduits, arti- 
ficial falls, thin films of water passing over large surfaces — in 
fact, any device that will permit the air to mingle with the 
waters — give new life to the waters and death to organisms. 
The plan adopted by the Utica (N. Y.) Water Company is on 
the fountain principle, discharging the water under pressure 
through a series of pipes, the aggregate areas presumably equal 
to the main discharge pipe, and into a shallow basin. The 
greater the pressure the greater the height the waters are 
elevated by their several columns, giving proportionately time 



742 COMPRESSED AIR AND ITS APPLICATIONS. 

for the action of the air on the ascending and descending waters. 
It occurs to one's mind, however, that the quantity of water 
thus treated should not be in excess of the daily amount used, 
that each day's supply of water should be fresh. This mode 
of purification of water will require treating reservoirs of shal- 
low depth and surface area equal to requirements. 

A similar plan to the Utica plant is the one at Fresh Pond, 
adjacent to the Stony-brook reservoir, at Cambridge, Mass. ; 
different in that four outlets of discharge are in use, and throw- 
ing the water into the air 40 feet above its outlet. 

THE PNEUMATIC CYANIDE PROCESS FOR THE EXTRACTION OF 

GOLD. 

The features of the "pneumatic" process are so easily un- 
derstood that it does not require an expert or a thorough chem- 
ist to appreciate them, for every mining man has had more or 
less experience with compressed air, and most of them know 
something about the cyanide process and understand that oxy- 
gen is absolutely necessary in a solution of cyanide of potassium 
in order to form a new compound, cyanogen, which is the true 




Fig. 527 —series of leaching vats, or tanks, fitted with pipes and valves for the 
introduction and control of the compressed air. 

solvent of the gold. They know also that agitation hastens the 
process of dissolving and extracting the gold values during the 
leaching process, because agitation, or stirring, enables the oxy- 
gen of the air to reach the solution more rapidly to form cyano- 
gen and also to bring the ore and solution into more intimate 
contact, and does in a few hours what it takes days to do if the 
ore and solution remain unmoved in the leaching vats. 

Many attempts have been made to stir or agitate the mass 



COMPRESSED AIR IN THE CYANIDE PROCESS. 743 

of leaching ore by machinery; but the great costs of power, ex- 
pensive construction, breakage of parts, etc., have caused 
them to be abandoned, and mill owners have gone back to the 
old slow process of letting the ore stand for days in the leaching 
vats because there was no practical and cheap way of agitating 




Fig. 5?8.— section through the leachixg vats. 

Showing the air pipes under the perforated bottom and the double trap-door in the bottom 
for discharging the leached refuse. 

them, or of getting the oxygen through the solution, except by 
the slow absorption from the atmosphere. 

Just at this time, when it seemed as if improvement in the 
cyanide process was at a standstill, the " pneumatic " process 
comes forward with a method so simple and so effective that it 
is a wonder that it was not thought of sooner. 

It is simply the introduction of strong currents of com- 
pressed air into the bottom of the leaching vats, which force 
their way upward bubbling and boiling through the mass of 
crushed ores and cyanide solution, and thus furnish both the 
oxygen and the agitation needed for the rapid and thorough 
extraction of the gold. This method of forcing the air through 
the leaching ores can be readily understood by means of the 
cuts shown. The air pressure required is small; no more than 
to overcome the hydrostatic pressure of the liquid and keep the 
air bubbling like boiling water. Reheating the air tends to 
warm the liquid and to facilitate the work. It amply pays for 
reheating the air. 

WOOD VULCANIZING. 

The process of vulcanizing wood by the Haskins system is 
about as follows : Large iron or steel tanks are arranged hori- 
zontally and of sufficient size to admit the charge of wood re- 
quired to be vulcanized. 



744 COMPRESSED AIR AND ITS APPLICATIONS. 

Coils of pipe are placed inside the tanks for the purpose of 
heating the air to the desired temperature of about 285 to 300 
F. The heating is usually done by steam. The wood is placed 
inside the pipe-line^ tanks and steam is turned on until the 
interior is heated to about 200 F. Then the openings are 
closed and compressed air is admitted up to 150 or 200 pounds 
pressure. The air is kept circulating around the wood at an 
average heat, the desired temperature being 285 to 300 F. 
for eight or ten hours. The circulation is accomplished by 
means of a circulating engine which takes the air out of the 
vulcanizing tank, passes it through a reheater and back to the 
tank. This process prepares the wood in such a way that it 
will last almost indefinitely. 

AGING OF LIQUORS. 

The purifying of alcoholic liquors is accomplished by com- 
pressed air through the Cushing process, which has been in 
vogue for many years. The liquor is placed in receptacles for 
the purpose, and air, after it has been washed and purified by 
Professor Tyndall's well-known method, is compressed and 
forced through perforated pipes entering the liquor in minute 
streams. The liquid is violently agitated and the air permeates 
every portion of it. The air being warm oxidizes the fusel oil 
and at the same time volatilizes and expels into the open air 
the light poisonous ethers, leaving the liquors thoroughly pure 
and free from aldehydes. It is claimed that by this process 
new liquor for medicinal purposes is made practically as good 
as old, and that the drinking of liquor treated thus does not 
cause stupefaction, headaches, and other disagreeable results. 



Chapter XXXIII. 



REFRIGERATION 



REFRIGERATION. 

REFRIGERATION BY THE VACUUM SYSTEM. 

This is generally known as the vacuum process, for as the 
refrigerating agent itself is rejected, the only agent of a suffi- 
ciently inexpensive character to be employed is water, and this, 
owing to its high boiling-point, requires the maintenance of a 
high degree of vacuum in order to produce ebullition at the 
proper temperature. The vapor tensions of water at tempera- 
tures up to boiling-point at atmospheric pressure are given in 
Table II., from which it will be seen that at 32 F. the tension 
is only 0.089 pounds per square inch. In ice-making, therefore, 
a degree of vacuum must be maintained at least as high as this. 
The earliest machine of this kind appears to have been made 
in 1755 by Dr. Cullen, who produced the vacuum by means of 
an air pump. In 18 10 Leslie, combining with the air pump a 
vessel containing strong sulphuric acid, for absorbing the vapor 
from the air drawn over, and so assisting the pump, succeeded 
in producing an apparatus by means of which from one to one 
and one-half pounds of ice could be made in a single operation. 
Vallance and Kingsford followed later, but without practical 
results ; and Carre many years afterward embodied the same 
principle in a machine for cooling and for making small quan- 
tities of ice, chiefly for domestic purposes. His machine, which 
is still sometimes used, consists of a small vertical vacuum pump 
worked by hand, either by a lever or by a crank, which exhausts 
the air from the carafe or decanter containing the water or 
liquid to be frozen or cooled. Between the pump and the water 
vessel is a lead cylinder, three-fourths full of sulphuric acid, 
over which the air, and with it the vapor given off from the 
liquid, is caused to pass on its way to the pump. The vacuum 



748 COMPRESSED AIR AND ITS APPLICATIONS. 

thus produced causes a rapid evaporation, which quickly lowers 
the temperature of the water ; and if the action is prolonged for 
about four or five minutes, the water becomes frozen into a 
block of porous, opaque ice. The charge of acid is about four 
and one-half pints, and it is said that from fifty to sixty carafes 
of about a pint each can be frozen with one charge. So long as 
the joints are all tight, and the pump is in good order, this 
apparatus works well ; but in practice it has been found trou- 
blesome and unreliable, and consequently has never come into 
anything like general use. 

In 1878 Franz Windhausen, of Berlin, Germany, brought 
out a compound vacuum pump for producing ice direct from 
water, on a large scale, without the employment of sulphuric 
acid; and also an arrangement in which sulphuric acid could 
be used, the acid being cooled by water during its absorption 
of the vapor, and afterward concentrated, so that a fresh supply 
was rendered unnecessary. This apparatus was improved on 
in 1880; and in 1881 a machine nominally capable of producing 
1 5 tons of ice per twenty-four hours was put to work experi- 
mentally at the Aylesbury Dairy at Bayswater, England. It 
consists of six slightly tapered, ice-forming vessels of cast iron, 
of circular cross section, closed at their bottom ends by hinged 
doors with air-tight joints, into which water is allowed to flow 
through suitable nozzles, the cylinders being steam-jacketed in 
order to allow the ice to be readily discharged. The upper 
parts of these vessels communicate with the pump through a 
long horizontal iron vessel of circular section containing sul- 
phuric acid, which, when the machine is in operation, is kept 
in continual agitation by means of revolving arms. The acid 
vessel is surround-ed with cold water, which carries off most of 
the heat liberated during the absorption of the vapor. The 
pump has two cylinders, one double-acting of large size, and a 
smaller single-acting one. The capacities of these cylinders 
per revolution are as 62 to 1 . The air and whatever vapor has 
passed the acid are drawn into the large pump, which partially 



REFRIGERATION. 749 

compresses and delivers them into a condenser. Here part of 
the vapor is condensed by the action of cold water, the remain- 
der passing along with the air to the second pump, where they 
are compressed up to atmospheric tension and discharged. The 
advantage gained by the use of a compound pump is due to the 
action of the intermediate condenser and to the compression 
being performed in two stages, by which the losses from the 
clearance spaces in the large pump are rendered much less than 
they would be if compression to atmospheric pressure were ac- 
complished in a single operation. The effect of the pump is 
said to be such that a vacuum of half a millimetre of mercury, 
or about 0.0097 pound per square inch, can be continuously 
maintained ; though in actual work about 2\ millimetres, or 
0.0484 pound per square inch, is as low as is necessary. The 
concentration of the acid is effected in a lead-lined vessel, in 
which is a coil of lead piping heated by steam, the pressure in 
the vessel being kept down by means of an ordinary air pump. 
No acid pump is needed, as the transfer from one vessel to an- 
other is effected by the pressure of the atmosphere. The com- 
paratively cool weak acid on its way to the concentrator is 
heated in an interchanger by the strong acid returning from 
the concentrator. Six blocks of ice, each weighing about 560 
pounds, are formed in about twenty minutes after starting, 
The charge of acid is said to serve for three makings of ice, 
after which it becomes too weak, and requires to be concen- 
trated. 

The water being admitted into the ice-forming vessels in 
fine streams offers a large surface for evaporation, and is al- 
most immediately converted into small globules of ice, which fall 
to the bottom and become cemented together by the freezing of 
a certain quantity of water that collects there. This water 
being in a violent state of ebullition, the ice so formed is not 
solid, but contains spaces or blow-holes, which, as soon as the 
block is discharged from the vessel, become filled with air and 
cause opacity. Several attempts have been made to produce 



750 COMPRESSED AIR AND ITS APPLICATIONS. 

transparent ice by the direct vacuum process, but so far with- 
out success. Distilled water, or water deprived of air, has been 
tried, and hydraulic pressure has been used for compressing the 
porous opaque blocks, but neither plan has been found practi- 
cable commercially. It would appear that the only way to make 
clear ice by the vacuum process is by forming it in moulds, 
subjected externally to the action of brine previously cooled by 
the evaporation of a portion of its water. The cost in this case 
would necessarily be greater; but the ice would be solid and 
transparent, and would consequently have a higher commercial 
value. The latent heat of liquefaction of water being 142. 6° F., 
the total heat to be abstracted in order to produce 1 ton of ice 
from 1 ton of water at 6o° F. is 382,144 F. pound units. Tak- 
ing the latent heat of vaporization of water at 32 F. to be 
1,091.7, it is obvious that 350 pounds must be evaporated to make 
the ton of ice. But in addition the sensible heat of evaporated 
water, which entering at 6o° would leave at about 32 , would 
have to be taken off ; and this would require the evaporation of 
about g\ pounds more, making a total of about 360 pounds, 
without allowance for loss by heat entering from without, which 
would be considerable. The total water actually used is given 
by Mr. Piper at 12 tons per ton of ice, including the quantity 
required for cooling purposes. The fuel consumption is stated 
to be 180 pounds of coal per ton of ice; but a much larger 
quantity is actually required. It is consumed in generating 
steam for driving the vacuum pump and the concentrator air 
pump, and for evaporating the water absorbed by the acid. 
According to Dr. Hopkinson, the cost of making 1 ton of opaque 
ice is 4s. (about Si); experience has shown that a much higher 
cost is required to cover the necessary expenses for repairs and 
maintenance. Windhausen's machine has not met with any 
extended application, owing no doubt to the opaque and porous 
condition of the ice produced by it, and to the large and cum- 
brous nature of the plant, which must doubtless require great 
care and supervision in working. 



REFRIGERATION. 75 I 

A vacuum apparatus for refrigerating liquids by their own 
partial evaporation, and for making ice, was brought out in 
1878 by James Harrison in England. Its chief feature is the 
revolving cylinder or pump, which affords a simple and effi- 
cient means of exhausting large volumes of vapor of low ten- 
sion, without incurring the loss from friction of ordinary piston- 
packings, and the trouble of keeping them tight and in good 
working order, while at the same time the first cost is much 
reduced. The pump consists of a hollow iron cylinder, revolv- 
ing on a horizontal axis, and divided into compartments by 
longitudinal partitions of L section. It is partially filled with a 
non-evaporable liquid, or one which evaporates only at a tem- 
perature considerably in excess of that at which the refrigerat- 
ing liquid is evaporated, and which is also chemically neutral 
to the vapor that is brought in contact with it. In practice, 
oil is the liquid used. The refrigerating or ice-making vessels, 
of any convenient form, are connected by a pipe with one end 
of a fixed hollow axle on which the cylinder revolves; and in- 
side the cylinder another pipe rises up above the level of the 
liquid, the longitudinal partitions being stopped short at one 
end to enable this to be done. The compartments move round 
mouth downward, carrying with them the vapor with which they 
are charged, and compressing it to an extent measured by the 
distance they dip below the surface of the liquid; until, when 
the lowest position is approached, the compressed vapor is 
liberated, and rises into a fixed hood near the centre, in com- 
munication with a second hollow axle at the opposite end of the 
cylinder to that at which the vapor enters. Through this sec- 
ond axle the compressed vapor passes to a surface-evaporative 
condenser, in which it is partly condensed by the combined 
action of direct cooling and the partial evaporation of water 
trickling over the surface; the water of condensation, together 
with any air, is then compressed to the tension of the atmos- 
phere by a small pump, and discharged. By this process it is 
expected to produce opaque ice on a large scale at a cost of 



752 COMPRESSED AIR AND ITS APPLICATIONS. 

about 25 cents per ton. The fuel consumption will certainly be 
very small, because friction, which is a large item in the Wind- 
hausen apparatus, is here to a large extent eliminated. There 
would also be a saving of all the fuel used in concentrating the 
acid, and of much of the water required for cooling purposes, 
besides a reduction in the first cost of the plant and in the ex- 
pense of maintenance. 

Although for nearly a half-century much attention has been 
given to the subject of cooling and refrigeration by the vacuum 
process, it has not proved a commercial success ; it is still feasi- 
ble for experimental work, and claims a space in the history 
of air work. 

COMPRESSED-AIR REFRIGERATION. 

THE EARLIEST ICE MACHINE. 

The earliest known appliance for making ice by compressed 
air seems to have been invented and put into actual practice 
by Dr. John Gorrie, of New Orleans, La., whose patent dates 
May 6th, 185 1, although ice was actually made in his machine 
at Apalachicola, Fla., in the summer of 1850. 

The machine consisted in its essential operating parts of an 
air-compressing cylinder and piston operated from a crank 
shaft by connecting rods. 

A small injection pump operated from a cam on the main 
shaft was so adjusted as to inject a small spray of cold water into 
the cylinder during the latter part of compression at each stroke 
of the piston, thus being the leading practical application of 
the injection system for cooling the air during compression ; the 
compressed air and injected water being driven together 
through the exit valves and through a coil of pipe immersed in 
a tub of cold water, to the receiver, from which the injected 
and condensed water was drawn off through a waste cock at the 
bottom. 

On the same platform and connected with a crank on the 



REFRIGERATION. 753 

main shaft, was located the expansion cylinder with its piston 
and connecting rods. 

The size of the expansion cylinder was made somewhat 
smaller than the compressor cylinder, to compensate for the 
decreased volume of air due to the difference between adiabatic 




Fig. 529 -the gorrie ice machine. 



and isothermal values in compression and expansion for both 
cylinders. 

The expansion cylinder was also provided with an independ- 
ent injection pump operated from a cam on the main shaft by 
which an injection of a non-freezing liquid (brine) was made, 
which, by the convection of its heat to the cold air, becomes a 



754 



COMPRESSED AIR AND ITS APPLICATIONS. 



cooling medium, and was carried with the cold air through the 
exit valves and connecting pipe into the cold reservoir sur- 
rounding the cylinder. 

The expansion cylinder was enclosed in a brine jacket with 
outlets for the cold exhaust and injection, through pipes 
terminating in the brine vat, for the purpose of utilizing the 
refrigerating effect of the expanded air for its full value ; the 
free air, finally permeating the ice-making chamber above, and 
an outer insulating case surrounding the brine tank and expan- 
sion cylinder, made its exit through a coil in an insulated tank 
for cooling the water to be frozen, which was drawn from the 
cooling tank into the freezing cans of the form much in the 
style as now used, and placed in the cold brine tank for the 
freezing operation. 

It may be seen from the amply illustrated description in the 
patent specifications, and from the testimony of persons that 




Fig. 530.— front elevation, ice machine. 



saw the apparatus, that Dr. Gorrie had conceived and put into 
practice a device almost perfect in principle for refrigeration 
by compressed air at least a score of years before it became a 
commercial factor in any form. 



REFRIGERATION. 



755 



The idea of using the terminal exhaust for cooling the water 
to be frozen to near the freezing-point was a most important 
one in the matter of economy. 

The whole apparatus as completed in 
1850 seems to have been the result of 
several years of study and experiment, 
and as now viewed was a most complete 
and advanced conception of the later 
developments of refrig- 
eration by compressed 
air as made by Lightfoot, 
Hall, Bell, and others in 
England and on the 
Continent, and by Hunt, 
Allen, and others in the 
United States; for, in 
leaving out some parts 
of Dr. Gorrie's machine, 
the principles of all the 
later machines are 
covered. 

A reference to our 
illustration will show the 




Fig. 531.— side elevation, ice machine. 



A, The air-compressing cylinder ; B, receiver or 
compressed-air tank; P, cooling tank with air-pipe 
coil P; D, injection pump for compressor spray, oper- 
ated by cam and bell crank ; C, the expansion cylin- 
der ; E, expansion cylinder injection pump, not shown, 
drawing brine from the jacket W and forcing it in a 
spray into the expansion cylinder, by which the brine 
is quickly cooled and discharged with the cold air into 
the upper section of the brine jacket and tank ; /, the 
freezing can or tank, shown in Fig. 530, above the in- 
sulated cylinder. 



details of construction of the compressed-air freezing apparatus 
of Dr. Gorrie ; the power for running the machine not being 
shown. A charging tank, containing fresh water for supplying 
the freezing can, is placed overhead. The other lettering in- 
dicates details readily understood by inspection. 



COMPRESSED-AIR REFRIGERATING MACHINE AS MADE BY 
J. AND E. FIALL, DARTFORD, ENGLAND. 

The machine consists of three cylinders, fitted with metallic 
pistons placed side by side, and connected by a crank shaft, 
common to all, by means of piston rods, crossheads with slipper 



756 



COMPRESSED AIR AND ITS APPLICATIONS. 



guides, and connecting rods, in the manner common with ordi- 
nary horizontal engines. The same crank shaft drives a water- 
circulating pump, and beneath the frame which carries the 
whole mechanism is a tubular refrigerator. The lower cylinder 
in Fig. 532 is of the kind ordinarily made for steam engines, 
and may be constructed with expansion valves, steam jacket, 
and all other accessories suitable for a steam engine of the best 
construction. 

The power developed in this cylinder is transmitted through 
to the crank shaft, by an overhung crank, to a centre crank, 
which actuates the piston of the middle or air-compressing cyl- 
inder, which is water-jacketed, and fitted with double slide 
valves, through which air is drawn in from the outside atmos- 
phere and delivered, compressed to about 45 pounds per square 
inch, and at a temperature of about 250 , to the tubular refrig- 
erator. The hot air circulates through a number of metal 
tubes, round the outsides of which passes a current of water 

^Circulating Pump 




Fig. 532.— plan, hall air-refrigerating machine. 



supplied by the circulating pump, actuated by the crank shaft. 
The water rises about io° in temperature, and carries off, in the 
form of heat, a portion of the energy of the steam engine. The 
compressed air, reduced to nearly the normal temperature and 
at a pressure of 45 pounds per square inch, next enters the 
upper cylinder on the diagram, through double slide valves, 
and is made to expand, doing work upon the piston, and there- 



REFRIGERATION. 



757 



fore its temperature falls in proportion to the amount of energy 
communicated to the crank shaft, which energy is applied to 
reduce the work to be done by the steam. The temperature 
of the air is reduced by this means to as much as 130 below the 
freezing-point. In some cases, instead of drawing air into the 
compression cylinder from the atmosphere, it is drawn from 




FIG. S33-— SECTION, HALL AIR-REFRIGERATING MACHINE. 



the refrigerated chambers, and is made to pass over a number of 
tubes containing the compressed air, which is thus cooled to a 
still lower temperature than was effected by the cooling water, 
the result being that a relatively lower temperature is obtained 
after expansion. Simple as the process appears to be, yet, to 
obtain the best results, great nicety is required in the propor- 
tions of the cylinders, in the extent to which the air is com- 
pressed, the degree to which the air is expanded, and in the 
practical details of the valve gear, which are especially impor- 
tant with respect to the difficulties attendant upon the forma- 
tion of snow and ice derived from the freezing of the moisture 
always contained in the air. It is the successful treatment of 
these details which makes the difference between an economi- 
cal and trustworthy machine and a wasteful or uncertain one. 
When applied to refrigerate the holds of vessels engaged in the 
dead-meat trade, the money value depending on the efficiency 
and trustworthiness of a machine is very large. 



758 COMPRESSED AIR AND ITS APPLICATIONS. 

Setting aside friction, the power necessary to drive the cir- 
culating pump, and the heat represented by radiation and con- 
duction, the useful work done by the steam is measured by the 
quantity of heat carried off by the water circulating round the 
cooling tubes and the compression cylinder. The theoretical 
amount of cooling is easily determined. 

The air under an absolute pressure of four atmospheres, and 
at a temperature a little above that of the surrounding atmos- 
phere, say at 6o°, is expanded along the adiabatic curve to one 
atmosphere; the absolute temperature at the end of the opera- 
tion will therefore be theoretically — 
520 



(^i ) 0.29 = 348 absolute, 



which is 144 below the freezing-point, instead of the 130° at- 
tained in practice. The air in expanding absorbs a certain 
amount of heat from the cylinder, and hence the slight dis- 
crepancy. 

In these machines about 50 per cent of the work of the 
compression piston is returned by the expansion piston as 
claimed when operated on cold air drawn from the refrigerat- 
ing room. 

THE ALLEN DENSE-AIR ICE MACHINE. 

The distinguishing feature of the Allen dense-air ice 
machine (the invention of Mr. Leicester Allen, of New York) 
is, that it takes for compression not air of atmospheric pressure 
from the open atmosphere or from cooled chambers not air 
tight, but air of considerable pressure which is contained in the 
machine and in a system of pipes. 

This air under pressure (generally 60 or 70 pounds) is taken 
in by an air compressor and compressed to commonly 210 or 
240 pounds. This heats up the air, storing in it such amount 
of heat as is the equivalent for the work expended upon the 
compression. It is then passed through a copper-pipe coil im- 



REFRIGERATION. 



59 



mersed in circulating water, which removes the heat to nearly 
the temperature of the water. 

Then the air passes into the valve chest of the expander, 
which is, in construction, a usual steam engine with a cut-off 
valve. The valves admit the highly compressed air upon the 
piston to a certain point of the stroke and then shut it off. The 
piston continues to travel to the end of the stroke, the air ex- 
erting pressure upon it (constantly diminishing). This takes 




Fig. 534.— air compressor and expander. 
Horizontal type of the Allen system. H. B. Roelker, 41 Maiden Lane, N. Y. City. 



out of the air such a quantity of heat as the work performed by 
the air, while expanding, requires for its performance. 

The result is a very low temperature of the air at the end of 
the stroke. The return stroke of the piston pushes it out 
through thickly insulated pipes to such places as are to be re- 
frigerated, viz., the ice-making box, the meat chamber, and 
the drinking-water butt. In all these the air is tightly enclosed 
in pipes or other strong apparatus, being under the original 
pressure at which it entered the compressor (60 or 70 pounds), 
when the cold is given out through the metallic surfaces. 

The machine usually consists of the following parts, refer- 
ring to Fig. 536: 



?6o 



COMPRESSED AIR AND ITS APPLICATIONS. 



A. The steam engine, which is of usual construction, and 
to its crank shaft the air compressor and the expander are 
linked. The expander helps the steam cylinder and the air 
compressor takes the power. 

B. The compressing cylinder, which is constructed with 




fek^a :^JJWg?7£ftit 



FIG. 535.— air compressor and expander. 
Vertical type of the Allen system. 



slide valves instead of the usual conical lift valves, in order to 
move more quickly and noiselessly. 

C. The copper coil placed inside, of a cylinder containing 
circulating water. In this the highly compressed air is cooled 
to nearly the temperature of the water. 



REFRIGERATION. 



761 



D. The expander cylinder, which is constructed like a usual 
steam-engine cylinder, with slide valve and cut-off valve. It 
must cut off the pressure at such a point that the expanded air 
at the end of the stroke of the piston is very nearly of the same 
pressure as the air contained in the system of pipes. If it were 
of much higher pressure it would, at exhausting, warm up 
again, by exerting its remaining power in producing velocities 
and frictions inside of the apparatus. 

E is a trap which gathers out of the cold air the lubricat- 




FlG. 536. -CYCLE OF COMPRESSED-AIR REFRIGERATION. 



ing oil which is used in the compressor and expander cylinders ; 
also some snow. It contains a jacket connectable to steam, in 
order to liquefy the frozen contents when they are to be blown 
out. 

F is the water pump which circulates water around the 
copper coil C, and through a water jacket which surrounds the 
working cylinder of the air compressor B, in order to prevent 
the heat from injuring the packings. 

G is a small air-compressing pump which takes air from 



762 COMPRESSED AIR AND ITS APPLICATIONS. 

the atmosphere and pushes it into the machine and pipe sys- 
tem. This charges the system with the requisite air pressure 
when the machine starts to work, and maintains the pressure 
against leakages occurring at the stuffing-boxes and joints. 
This air contains the usual atmospheric moisture ; and to expel 
this, the outlet pipe from this pump passes the air through the 
trap H, where it is cooled by being forced into very close con- 
tact with the cold head of the reservoir for coil C. This cooling 
under pressure and contact with moist surfaces deposits out of 
the air about 80 or 85 per cent of the contained moisture, 
which is then drained off by pet-cocks, leaving pure air for the 
refrigerating work. This is of great importance, as the large 
amounts of latent heat in the water vapor and of latent cold in 
frozen water would produce very serious losses in the result of 
the machine if the air contained water, which would be subject 
to the heating and freezing processes which occur in the ma- 
chine. Surplus air is blown off by a small safety valve. 

The air pistons are packed with leather soaked in castor oil. 

The air stuffing-boxes contain, first, a few rings of Katzen- 
stein soft metal packing rings, then a hollow oiling ring, then 
outer layers of fibrous packing, usually square Garlock packing. 
The oiling ring is kept full of oil by a sight-feed pressure lubri- 
cator which is connected by a pipe to the stuffing-box. 

The air pushed out by the expander is practically of about 
— 35 to —55 F., depending upon the temperature of the cool- 
ing water and upon internal leaks and frictions. The pipes 
lead it first through oil trap E, for purification, then to the 
ice-making box /, which consists of a casting, forming pockets 
T, for the reception of sheet-iron ice cans. This casting is set 
in a strong and tight-jacket casting with internal bulkheads, 
formed so that the cold air which is led into the space between 
jacket and ice-can pockets must pass closely along the surfaces 
of the pockets. 

The small space between the sheet-iron ice cans and the 
inside of the pockets is filled with a solution of about equal 



REFRIGERATION. 763 

weights of chloride of calcium and water, which withstands the 
cold without freezing. It provides a good conductor for the 
cold and keeps the cans from freezing fast in the pockets. 

For larger apparatus, a wrought-iron tank, filled with re- 
frigerating pipes, and ice cans, all immersed in the above brine, 
are used. 

From the ice-making box the cold air is led to the meat 
chamber K, where it is passed through a system of refrigerating 
pipes L. 

Frozen meat can be kept practically without change for an 
almost indefinite time. When kept at nearly the freezing-point 
without change it will remain for a number of weeks in good 
condition. A good practical rule for the amount of refrigerat- 
ing pipes required in the meat chamber to keep this at the 
freezing-point is: One square foot of pipe surface for every 
2^ to 2| square feet of interior surface of well-insulated meat 
chamber, omitting interior divisions. It is necessary to arrange 
the pipes so that the air in them is compelled to pass all sur- 
faces with fair velocity. 

From the meat chamber the cold air goes to the refrigerat- 
ing pipes in the drinking-water butt M, passing first to the 
bottom layer and then gradually upward. 

After that it returns to the compressor inlet of the ma- 
chine. 

In arrangements where all the cold is not taken out of the 
air by the refrigerator apparatus, the highly compressed air 
after cooling in the copper coil is further cooled in a special 
apparatus, where it is brought into surface contact with the re- 
turning and still cold air, before entering the expander. 

Temperatures of 70 to 90 below zero are thus practically 
obtained in these machines. 

It is of the greatest importance that all apparatus containing 
artificially cooled air or brine should be very heavily insulated 
with air-tight and waterproof material, because the water vapor 
of the atmosphere is attracted with great force to all cold sur- 



764 COMPRESSED AIR AND ITS APPLICATIONS. 

faces, destroying fibrous materials as soaking them in water 
would do, and consuming much cold by its latent heat. 

The vertical machines have the same parts as the horizontal 
machines, only of different dimensions and different detail of 
position. 

COLD STORAGE AND COLD ROOMS FROM THE DIRECT EXPANSION 
OF COMPRESSED AIR. 

In view of the largely increasing demand for the means of 
preserving food in the warmer sections of the United States, 
and in tropical climates, where ice cannot be obtained or the 
cost is so great as to preclude its use, the expansion of com- 
pressed air as a constant cooling medium is one of the means at 
the command and control of every one who is able to place a 
small outlay for a valuable boon to household comfort; and 
for the profit that may be realized from the power to preserve 
fruit, vegetables, and meat for sale, or for the time and oppor- 
tunity for shipment to a market. 

There are large tracts of country in the southern section of 
the United States in which are situated plantations and farms, 
the owners and managers of which, having the financial means 
to supply comforts to life by the use of cold preserved food, 
yet are entirely beyond the reach of ice, either natural or arti- 
ficial; with them, such wants may be supplied by means of any 
small power, such as a windmill, a waterfall, a gasoline or oil 
engine, operating a pump for the compression of air. In Mexico 
and the Central American and South American States, the 
field for useful work by wind and water power alone for con- 
tributing to domestic comfort by the preservation of food is im- 
mense ; where power from nature as through a windmill or 
water wheel can be utilized. The distance need not be consid- 
ered beyond the cost of a small pipe for conveying the com- 
pressed air, as a considerable length is needed to cool the air 
to its normal temperature when it has been heated by the opera- 
tion of compression ; when by expansion to atmospheric press- 



REFRIGERATION. 



765 



tire an approximate amount of heat may be eliminated from 
the expanding air as was accumulated by its compression, and 
from which a large cooling efficiency may be obtained. 



Compression Volume 




FIG. 537.— theoretical diagram of isothermal air compression and adiabatic expan- 
sion FROM VARIOUS PRESSURES AND NORMAL TEMPERATURE OF 60° F. 



The graphic diagram (Fig. 537) has been made to show at 
sight the theoretical cooling effect produced by the free expan- 
sion of dry air from various pressures and from the normal 



J66 COMPRESSED AIR AND ITS APPLICATIONS. 

temperature of 6o° F. The conditions of air expansion for any 
natural temperature of the stored air may be found by simply 
subtracting the difference from the expansion column when nor- 
mally above 6o°, or adding when below 6o°. Thus, in an at- 
mospheric temperature of 8o°, the cold produced by expanding 
from 20 pounds pressure would be — 67 instead of — 87 , as 
shown in the diagram. From 50 pounds pressure and 90 at- 
mospheric temperature, the cold air of expansion would be 
— 108 instead of — 138 , as in the diagram; thus for any at- 
mospheric condition of temperature and pressure, the theoreti- 
cal condition of cold by expansion may be known by simple 
inspection of their several relations as shown in the diagram. 

The diagram shows much that is interesting in regard to 
the general conditions and effect of air compression and expan- 
sion. It will be seen that the column of pressures on the right 
corresponds with the column of heat developed by compression 
on the left, while the upper or adiabatic curve shows the condi- 
tion of temperature, pressure, and volume at the moment of 
compression. The lower or isothermal line shows the shrink- 
age of the volume due to the cooling of air to its normal tem- 
perature. 

The vertical dotted lines from the intersection of the iso- 
thermal line with the horizontal lines of pressure, meeting the 
atmospheric line from the starting-points for the curves of ex- 
pansion, are extended on the same scale of temperature corre- 
sponding with the scale of compression. 

The intersections of the dotted lines extended through the 
curved lines of expansion show also in a graphic way the frac- 
tional expansions from one stage of compression to another 
lower one, as measured by the expansion scale at the left-hand 
side. Thus when a volume of air at 60 pounds pressure and 6o° 
temperature is expanded to 30 pounds pressure, its temperature 
will fall to the intersection of the extended dotted line of 30 
pounds pressure with the 60-pound curve, which measured on 
the expansion scale is — 57 ; and so on for any other pressures. 



REFRIGERATION. 767 

In applying the conditions of air expansion to the practical 
effects of refrigeration or the cooling of rooms for cold storage 
and preservation of food, a large deduction from the theoretical 
figures for the degree of cold by air expansion must be made 
for success. 

The absorption of heat from the walls of a cold room, the 
cooling of a large body of air in the room and of food products 
stored, and the greater loss from frequent opening of a cold 
room for the removal and refilling, with the natural leakage of 
cold air around the doors, make the margin of loss in cold-air 
production a larger one than at first appears when brought into 
actual use. 

The amount of heat contained in a given volume of air is 
about ^j4"4 of the amount contained in the same volume of wa- 
ter from any number of degrees change of temperature at ordi- 
nary climatic temperatures ; so that there is a large margin be- 
tween the volume of cold air required to cool a room filled with 
air only and the volume required to cool a room filled with fruit, 
vegetables, milk, butter, or meat containing from 50 to go per 
cent of water, and of which the solid parts also have a far 
higher specific heat than air. 

This property of water-loaded food accounts for the time re- 
quired to cool a loaded cold-storage room over the time required 
for cooling an empty one, as well as the necessity for so pack- 
ing the material of storage that the cold air can circulate freely 
and bring every part to the required temperature in the short- 
est possible time. 

As to the work that compressed air will do in cooling rooms, 
there is a large marginal range in the quantity of free air re- 
quired for a specific temperature, due to the conditions of tem- 
perature of the material to be cooled and the amount of com- 
pression in the air to be expanded for this duty, less the work 
duty of expansion and the losses by radiation and leakage. 

Assuming, for example, a cold room for a farm or plantation, 
of 1,000 cubic feet capacity, or say 12 feet square by 7 feet high, 



768 COMPRESSED AIR AND ITS APPLICATIONS. 

thoroughly insulated, with a double door at side for storing ; a 
single or trap door with a small ventilator at top, with steps, 
from the trap door for every-day use, and also lighted from the 
top (by this means a loss of cold air is prevented by its 
greater specific gravity holding it at the bottom). The room 
may be kept uniformly at 36 F. in an outside temperature 
averaging 8o°. To cool such a room without storage material, 
from 8o° to 36 requires a loss of 46 ° in a volume of 1,000 cubic 
feet of air, say yy pounds, the specific heat of which is 0.2375 
water = 1. Then yy X 0.2375 = l %- 2 heat units must be ab- 
sorbed for every degree of change in temperature. Then 18.2 
X 44 = 800 heat units must be abstracted to bring it to 36 
F., leaving out the cooling of the walls, displaced air, and leak- 
age, which will be only a matter of time in the initial operation. 
Assuming to use an air pressure of only 30 pounds per 
square inch, then in the graphic diagram, tracing the dotted 
line from the isothermal curve junction of 30 pounds and fol- 
lowing its curve of expansion, we have — 138 -f- 6o° to the at- 
mospheric temperature = 198 difference in temperature to be 
overcome by expansion from 30 pounds pressure, or 198 heat 

units per pound of air. Then = 4 ' 4 , or 17 pounds X 

198 -2375 

13. 1 = 223 cubic feet of free air at 30 pounds pressure will be 
required to cool the room to 36 . 

A compressor of 5 cubic feet per minute capacity, using less 
than 1 horse power, will furnish enough air to reduce the tem- 
perature of the room from 8o° to 36 , in which the displacement 
of air in the room by the addition of 223 cubic feet of cold air 
should nearly neutralize the loss of effect by resistance and ra- 

diation, when the theoretical time — ^ = 45 minutes may be 

doubled to about i-|- hours, and should then easily furnish cold 
air for absorption of heat from the material of storage and to 
supply the waste made necessary by ventilation and radiation 
with a constant work of less than a half horse power. This 



REFRIGERATION. 769 

power comes within the scope of a cheap class of water wheels, 
water motors, and the smaller sizes of gasoline and oil engines 
and windmills. 

Where intermittent power must be used, as with windmills 
and power engines, a system of storage of compressed air may 
be used with perfect satisfaction as affording a constant flow of 
air into the cold room and also into a small refrigerator, which 
will be found a most useful adjunct for household use for cool- 
ing drinking-water. 

The amount of pipe surface required for cooling compressed 
air to the normal temperature is a matter of much importance, 
as its delivery at the point of expansion, to be effective, must 
be at, or very near, the temperature of the outside atmosphere. 

The method of keeping the air-cooling pipe at the proper 
temperature fixes the amount of pipe surface to be provided. 

For 30 pounds pressure, 15 square feet of cooling surface 
per cubic foot of free air used per minute is a fair proportion 
for an air-cooling coil exposed to a free circulation of the at- 
mosphere and shaded from the sun's heat. 

This would indicate a coil of 150 feet of ii-inch pipe for the 
requirement of a cold room as above stated, which may also in- 
clude the leading pipe from compressor to cold room, if favor- 
ably situated for cooling. Where it is convenient to use water 
for cooling, either by a sprinkler or by submerging the coil in a 
tank of water fed from a stream or by pumping, the size of the 
coil may be greatly reduced, according to the temperature of 
the water. 

For an intermittent power as a windmill, or a gasoline en- 
gine that would not be convenient to run at night, a storage of 
air will be necessary by the use of a proportionally increased 
power during the day for accumulating compressed air in tanks. 
For night cooling, after the room has once been brought down 
to the required temperature, the quantity of air per hour will be 
much lessened, so that the estimated storage of sufficient air 
for a ten-hours' run of the above plant will require tanks to 
49 



yjO COMPRESSED AIR AND ITS APPLICATIONS. 

hold about 1,200 cubic feet, or say 3 tanks of cylindrical form 
5 feet diameter, 21 feet long. As the atmospheric temperature 
always falls at night in tropical and semi-tropical regions, the 
conditions of compressed-air supply may be much modified in 
the storage quantity above outlined by partially closing the air- 
inlet valve; and where constant power can be obtained, the 
whole question of cold storage for private use becomes a cheap 
and simple one. 

The arrangement of the nozzle or orifice for delivering the 
compressed air, and at which point the expansion takes place, 
is important, and requires its area to be exactly gauged to the 
proper size for the delivery of the desired volume of air at the 
assigned pressure. At 30 pounds pressure, air flows through 
an orifice in a thin plate at the rate of 525 feet per second. 
Then for the plant as above described, for the issuance of 5 cu- 
bic feet of free air per minute under a compression of 3 volumes 

0.02777 cubic feet of compressed air per sec- 



3 X 60 

ond, and "' ' ' = 0.0000529 of a square-foot area. Then 

5 2 5 
0.0000529 X 144 = 0.0076176 of a square inch. Then enlarg- 
ing for the coefficient of efflux, the orifice should be i-inch di- 
ameter, with a needle valve in it to adjust or to shut off the air 
flow when required. Means should also be provided for blow- 
ing off any water that may condense in the air pipes or storage 
tanks by the cooling of the air after compression. 

With proper care and a moderate outlay the system of cold 
storage by compressed air becomes a simple, efficient, and eco- 
nomical adjunct to the living comforts of every home in a 
warm climate not blessed with a nearby ice-making plant. 



COOL WATER FOR DRINKING IN THE MACHINE SHOP. 

Mr. Frank Richards in The American Machinist has made the 
following suggestion for obtaining this desirable comfort, in 
shops using compressed air : 



REFRIGERATION. 771 

" A vertical cylindrical reservoir should be provided and 
connected to the water supply. This reservoir would be con- 
stantly full of water, and while contained therein the cooling of 
the water would take place. The water should enter the reser- 
voir at the top, and be drawn off at the bottom, and the draught 
pipe after leaving the reservoir should be as short as possible, 
so that the water after being cooled may not have a chance to 
warm up again. The cooling of the water would be accom- 
plished by the passage of expanded air through a coil of pipe 
closely surrounding the reservoir, the air entering at the bottom 
of the coil, and escaping at the top. The air should be brought 
to the cock which controls the admission to the coil at full press- 
ure, say, 70 to 80 pounds gauge, and at the temperature of the 
surrounding air. The compressed air, while under full press- 
ure and before reaching this point, should have been allowed 
to deposit all the moisture it could get rid of by passing through 
a suitable chamber or air receiver after being thoroughly 
cooled. A receiver near the compressor, and through which 
the air passes before it is entirely cooled, serves to equalize the 
pressure against sudden fluctuations, but it does not get rid of 
the moisture. A chamber through which the air may pass 
after it is thoroughly cooled will do so. As the air comes to 
the coil under pressure, and at normal temperature, upon being 
released from pressure, and flowing into the coil at atmospheric 
pressure, and expanded to four or five times its previous vol- 
ume, it is much lowered in temperature, and immediately be- 
gins to draw h.eat from the walls of the water reservoir which 
it encircles, thereby cooling the water contained in the reser- 
voir. The air coil instead of surrounding the water reservoir 
may be entirely within it, and directly in contact with the wa- 
ter. The latter is the better arrangement, but in either case 
the entire air coil and water reservoir must be enclosed in a 
thoroughly effective non-conducting jacket or covering. 

"Now, the getting of this coil and reservoir and all that, 
and rigging it up properly, is too great an undertaking, and 



772 COMPRESSED AIR AND ITS APPLICATIONS. 

one that few will be likely to undertake at first, so we have to 
suggest a way of doing it all with such material as is generally 
available, and which, because we have it handy, we generally 
assume to cost nothing. Take a i^-inch pipe ioo feet long — 50 
feet might be long enough — place it horizontally, and connect 
one end of it to the compressed-air supply with a suitable cock 
to. control the escape of the air. Leave the other end of the 
pipe open and enclose the whole of the pipe, after passing the 
air-admission cock, in a thick non-conducting covering. If you 
have nothing better at hand take plenty of paper, winding it on 
layer after layer and covering the whole pipe. Then lead a 
-f-inch water pipe into the open end of the air pipe, and let it 
come out by a tee or otherwise at the other end of the air pipe, 
and you have the whole apparatus. The air in this case, as be- 
fore, should be brought to where it is to be used thoroughly 
cooled and with all its water discharged." 



Chapter XXXIV. 



THE HYGIENE OF 
COMPRESSED AIR 



THE HYGIENE OF COMPRESSED AIR. 

It is more than half a century since the properties of com- 
pressed air as a remedial agent were put forward as a theory and 
in practice in "compressed-air baths," and claimed to be espe- 
cially useful in the treatment of pulmonary diseases and of dys- 
pepsia. As the pressure employed in the air baths was com- 
paratively slight, usually from 8 to 10 pounds per square inch, 
the effects observed differed widely from those produced by the 
high pressure employed in engineering and submarine work. 
This difference is not only in degree but also in kind, and 
therefore the literature relating to compressed air as a remedy, 
although extensive and interesting, throws no light upon the 
effect of high pressure upon the human system. 

It is only in the actual work of caisson sinking and diving 
in submarine work that reliable conditions as to the influence 
of compressed air on our vital condition have been observed. It 
is noted that at three atmospheres absolute, 30 pounds gauge 
pressure, it is impossible to whistle ; that in compressed air 
at considerable tension, every one speaks through his nose; 
that men under air pressures in ascending caisson ladders were 
much less out of breath than with the same work in the open 
air. 

In speaking, the tongue moves stiffly and with difficulty. 
Sounds are not heard with their usual intensity. The secretion 
of urine is decidedly increased. 

The most usual affection is muscular pains, occurring either 
alone or ushering in other symptoms. When, through lack of 
proper ventilation, the caisson air becomes impregnated with 
the smoke of lamps and carbonic-acid gas from respiration, all 
pathogenic conditions become intensified. 



7J6 COMPRESSED AIR AND ITS APPLICATIONS. 

Experience has taught that the ill effects are in proportion 
to the rapidity with which the transition is made from the com- 
pressed air to the normal atmosphere. 

Under pressures of 40 to 50 pounds per square inch, taste, 
smell, and the sense of touch lose their acuteness. 

During the time pressure is increasing the hearing is affect- 
ed, with a feeling of increasing warmth in the skin, as if going 
into a warm room. The pulse becomes small and thready, 
sometimes imperceptible. Venous blood becomes of a bright 
red hue. The lungs seem to increase in development, while 
the motion of the ribs is reduced. Shortness of breath is occa- 
sionally produced; increase of appetite is experienced, seldom 
thirst. 

While the pressure remains stationary, all subjective phe- 
nomena disappear, to return again during locking out from a 
caisson, when ringing of the ears and bulging of the ear-drums 
are observed ; taste and smell return ; a prickling sense of 
warmth is felt in the nostrils, which is sometimes followed by 
bleeding at the nose. At the same time the rapid decline of 
the temperature from the expansion of the air causes extreme 
chilliness. 

On going out from a caisson, intense pains in the ears and 
muscles sometimes occur, which are much modified or avoided 
by a slow change of air pressure. 

A good rule has been established to allow of five minutes 
for locking out from 7 pounds pressure ; seven minutes from 
15 pounds; ten minutes from 20 pounds; twelve minutes from 
30 pounds, and so on, with proper increase of clothing to 
counteract the chill from the decreasing pressure in the air lock. 

A serious inconvenience is experienced by workers in cais- 
sons, where gas or lamps are used, from theunconsumed carbon 
or smoke floating in the dense air. Its inhalation produces 
more or less irritation of the air passages and gives rise to a 
very characteristic black expectoration, which often continues 
for a long time after the caisson work is finished. 



THE HYGIENE OF COMPRESSED AIR. JJJ 

Comparative immobility of compressed air from its density, 
•which retards the velocity of the air currents necessary to per- 
fect combustion, has been assigned as the cause of smoky lamps 
and gas-jets in caisson work. A watch beats slower in com- 
pressed air. 

The following abstract from the prize essay of Andrew H. 
Smith, M.D., on the effects of high atmospheric pressure in 
caissons, is of great value to workers in compressed air: 



EFFECTS OF COMPRESSED AIR. 

The effects of a highly condensed atmosphere upon the 
system may be divided into those which are physiological or 
consistent with health, and those which are pathological and 
constitute or induce disease. 

The physiological effects will be considered according to 
the organs or functions in which they are exhibited. 

Effect on the Hearing : It is a law of acoustics that within 
the limit of mobility the denser the medium through which the 
soundwaves are communicated, the larger the wave, and there- 
fore the louder the sound. This supposes, of course, that the 
ear itself remains under normal conditions. Such, however, is 
not the case when the observer is in a highly condensed atmos- 
phere. The unusual pressure upon all parts of the auditory 
apparatus opposes a mechanical obstacle to the freedom of 
vibration, which is essential to perfect hearing. Hence, al- 
though larger sound waves may strike upon the ear-drum, 
feebler impressions are communicated to the auditory nerve, 
and the sound appears to be fainter than in the open air. Thus 
by repeated experiments, I found that a watch that could be 
heard distinctly at a distance of eighteen inches in a very noisy 
place in the open air, could not be heard at a greater distance 
than two inches in the comparative silence of the caisson. 

At the same time the velocity of the waves of sound is 
greater, and hence the pitch is higher. A deep bass voice is 



778 COMPRESSED AIR AND ITS APPLICATIONS. 

changed to a shrill treble, and the prolonged, heavy sound of 
a blast is so modified as to resemble the sharp report of a pistol. 

This modification of sound is very striking, and is almost 
the only thing to remind the casual observer that he is moving 
about in an atmosphere three or four times as dense as that to 
which he is accustomed. 

A curious fact, noticeable under these circumstances, and one 
which was long ago observed in diving-bells, is that it is im- 
possible to whistle. The utmost efforts of the expiratory mus- 
cles is not sufficient to increase materially the density of the 
air in the cavity of the mouth, and hence on its escape there is 
not sufficient expansion to produce a musical note. A similar 
difficulty, though in a less degree, is experienced in speaking, 
and for this reason protracted conversation is very fatiguing. 

Effect upon Respiration : In a highly compressed air, the 
frequency of the respiration is increased. Dr. Jaminet gives 
the rate as 21 per minute, with a pressure of 33 pounds, which 
accords with my own observations. He ascribes this increase 
of three or four per minute to an increased absorption of oxygen. 
Experiments show, however, that simply increasing the supply 
of oxygen diminishes the frequency of respiration instead of in- 
creasing it. The true explanation, I think, is to be found in 
the fact that the quantity of carbonic acid held in solution by 
blood, as by water, is in proportion to the pressure to which the 
gas is subjected ; and hence with the pressure existing in the 
caisson, the elimination of carbonic acid from the blood would 
not be as perfect as under normal circumstances, unless the air 
iu the lungs were more frequently changed. As observed by 
Francois and Dr. Jaminet, the depth of the inspirations is also 
increased. 

Effect upon the Circulation: It has been shown by numer- 
ous observers that under a slightly increased pressure, such as 
is employed in compressed-air baths, the pulse loses in fre- 
quency from the first. This is doubtless due to an increased 
absorption of oxygen by the blood, which thus affords a suffi- 



THE HYGIENE OF COMPRESSED AIR. 779 

cient supply to the tissues without the necessity of keeping up 
the usual activity of the circulation. In the course of some 
experiments undertaken nearly four years ago, I demonstrated 
that the same effect results under a normal pressure from add- 
ing oxygen to the air inhaled. But as the pressure increases 
the question is transferred from the domain of chemistry to 
that of mechanics. The condensation of the tissues from the 
pressure to which they are subjected, and the consequent nar- 
rowing of the vessels, oppose a physical obstacle to the circula- 
tion, which is felt before the blood has time to become sur- 
charged with oxygen, and while there is still a necessity for an 
active circulation. The labor of the heart is thus increased, 
and its action, in consequence, excited. I have frequently 
seen the pulse rise to 120 immediately upon entering the cais- 
son, where the pressure was from 30 to 35 pounds to the inch. 
But after the lapse of a period varying in different cases 
from half an hour to two hours, the pulse falls back to its nor- 
mal standard, or even, it may be, below it. The' blood has 
now became saturated with oxygen, and consequently a less 
active circulation is demanded. 

Doubtless, if the pressure were very gradually admitted, 
the preliminary rise in the pulse would not take place, the 
favorable chemical action keeping in advance of and counter- 
acting the unfavorable mechanical conditions. 

The effect of high atmospheric pressure upon the volume of 
the pulse is always, according to my observation, to diminish 
it. This is easily accounted for by the pressure exerted upon 
the artery, which prevents its yielding readily to the expanding 
force of each successive wave of blood. Hence, the pulse is 
small, hard, and wiry. These characteristics are independent, 
in a great degree, of the frequency of the beat, although as the 
heart recovers from the irritable condition into which it is 
thrown by the sudden increase of the pressure, and settles 
down, so to speak, more calmly to its work, it contracts with 
more force, and the pulse gains somewhat in volume. 



780 COMPRESSED AIR AND ITS APPLICATIONS. 

It is remarkable that the wide variations in the pulse-rate 
observed were not accompanied by any symptoms appreciable 
to the individual. A man with a pulse of fifty-two, and an- 
other with one of one hundred and sixteen, felt equally well, 
and each was entirely unconscious of anything unusual in the 
heart's action. 

The effect of the pressure upon the cutaneous vessels is 
shown by the pallor of the face, which is very marked, and 
continues for fifteen or twenty minutes after leaving the cais- 
son. The hands, too, feel shrunken, and the palmar surface 
of the fingers is often shrivelled, as if soaked in water. The 
pressure acting upon all sides of the fingers empties them to a 
considerable extent of blood, rendering the skin apparently too 
large for them. The veins, too, on the back of the hand seem 
to be effaced. 

Effect upon Temperature : In none of the reports upon the 
effects of high pressure as employed for engineering purposes, 
have I been able to find any records of temperature. J. Lange, 
however, found that under the comparatively slight pressure 
which is used as a remedy, the temperature of the body suffered 
a slight decrease. This is, no doubt, due to an increased ab- 
sorption of oxygen, which has been shown by Mr. Savory and 
also by experiments of my own to produce this effect. 

The temperature of the body in health is kept at about 98. 6° 
F., by the constant evaporation from the surface. But in the 
caisson, as already mentioned, the air was always nearly or 
quite saturated with moisture, so that evaporation from the 
surface must have been practically suspended. With the tem- 
perature of the air at 76 , as it was at the time of the observa- 
tions, and the men engaged in severe labor, it is easy to see 
how the absence of the cooling process of evaporation from the 
surface would lead to a rise of one degree of the thermometer. 
This view is strengthened by the result of three observations 
on a subsequent occasion, when the temperature in the caisson 
stood at 8i° instead of y6°. The average in this instance was 



THE HYGIENE OF COMPRESSED AIR. ;8l 

ioi°. A rise of five degrees in the temperature of the air could 
not sensibly affect the rapidity of tissue-change, but, if not 
counteracted by evaporation from the skin, it would soon tell 
upon the temperature of the body. 

The influence of the hygrometric condition of the atmos- 
phere upon the temperature of the body is a matter of daily 
observation. On a clear, dry day, with a high barometer, we 
are surprised to find the thermometer indicating a temperature 
much higher than our sensations would lead us to expect, 
while on the contrary, on a cloudy day, with a low barometer, 
we can scarcely persuade ourselves that the temperature is not 
many degrees higher than the thermometer indicates. In the 
dry, clear air of New Mexico I have supported a temperature 
of iio°, without inconvenience, while in the humid atmosphere 
of the Florida Keys I have found it almost unbearable at 86°. 

Effect upon the Perspiratory Function : Several writers have 
observed that it is immediately remarked by every one entering 
a caisson that the secretion from the skin is apparently im- 
mensely increased. It is noticeable even when the temperature 
of the air is moderate, but as this increases it becomes a very 
serious annoyance. The clothing quickly becomes saturated, 
which, besides the discomfort it occasions, exposes to great 
danger of taking cold on going out into the open air. 

But a little examination served to show that in the New 
York caisson, at least, there was really no increase of the secre- 
tion from the skin, but that, instead of evaporating, the moist- 
ure accumulated upon the surface, and thus stimulated excessive 
sweating. This was owing to the moist condition of the atmos- 
phere already mentioned, which rendered the drying of the 
surface by evaporation impossible. The atmosphere possessed 
to an extreme degree the quality of "mugginess," and the ap- 
parently profuse perspiration was merely an exaggeration of 
what we suffer from in very damp weather, even though the 
temperature be not extreme. 

So far from the perspiratory glands being stimulated by 



782 COMPRESSED AIR AND ITS APPLICATIONS. 

the density of the atmosphere, it is probable that the anaemia 
of the skin already described, as resulting from the pressure 
upon the surface, would tend to lessen the secretion by dimin- 
ishing the supply of blood to the glands. 

That there is not an undue amount of fluid carried off 
through the skin, is shown by the absence of thirst so generally 
remarked. 

The foregoing explanation of the apparent increase of per- 
spiration is important, as it bears upon the theory of excessive 
waste of tissue, in which the perspiration is supposed to aid. 

Effect upon Digestion : Nearly all authors who have written 
upon the effects of compressed air agree in stating that for a 
time, at least, it increases the appetite to a remarkable extent. 
Indeed this is one of the first and most favorable results ob- 
served where compressed air is applied remedially. With this 
experience my own observations in the main agree. It was 
frequently remarked by the men working in the New York 
caisson that their work made them unusually hungry, that they 
"could not get enough to eat," etc. Of course, it was not pos- 
sible to obtain any exact data as to the relative amount of food 
consumed, but from careful inquiries I arrived at the conclusion 
that it was considerably in excess of what is usual in the case 
of men engaged in similar labor in the open air. Still, there 
were many exceptions to the general rule, especially among 
those who had been long engaged upon the work, and whose 
general tone was beginning to deteriorate. Among these, loss 
of appetite was often complained of. 

The fact of this generally increased appetite seems to point 
to an increased waste of tissue, to be supplied by a greater con- 
sumption of food. An increased absorption of oxygen, such as 
we assume to take place, seems from the observations of several 
authorities to imply greater activity of tissue change as the 
ultimate result. But in this case I think it is scarcely safe to ac- 
cept this explanation at once as conclusive and sufficient. It may 
well be questioned whether during the actual sojourn in the 



THE HYGIENE OF COMPRESSED AIR. 783 

caisson the functions of digestion, absorption, and assimilation 
proceed normally under the wide departure of the system from its 
natural conditions. If it could be shown that a considerable por- 
tion of the food taken before entering the caisson is but imper- 
fectly digested or assimilated, the subsequent hunger would be 
readily accounted for. I am not aware that this point has ever 
been investigated, but I can scarcely believe that such an in- 
crease of appetite as is described could depend wholly upon in- 
creased interstitial change without giving rise to marked eleva- 
tion of temperature and other symptoms denoting unusual 
chemical activity. 

Effect upon the Urinary Secretion: Dr. Jaminet, in his ob- 
servations at St. Louis, found that the amount of fluid secreted 
by the kidneys was very much increased, in some instances 
nearly doubled, while the specific gravity was but little, if at 
all, below the usual average. This shows that the solid matter 
excreted was also in much greater quantity than usual. But I 
cannot agree with him in attributing this exclusively to the ex- 
cessive waste of tissue from over-oxidation of the blood. The 
explanation is to be found, I think, chiefly in the fact that the 
skin, as already stated, performs its function very imperfectly, 
owing to the impossibility of evaporation from the surface when 
the air is already loaded with moisture, and hence a portion of 
its duty is forced upon the kidneys, organs always ready to act 
vicariously for the skin or the mucous surfaces. 

Furthermore, the excretion of a large amount of urea indi- 
cates a relatively deficient oxidation of tissue, and is one of the 
characteristics of those diseases in which respiration is suddenly 
embarrassed, as, for instance, pneumonia. 

Another circumstance not to be lost sight of is, that the 
pressure upon the surface acts mechanically to congest all the 
abdominal viscera, and that congestion of the kidneys, within 
physiological limits, produces increased secretion of urine. 



Chapter XXXVI. 



PATENTS 



so 3 



PATENTS. 

ISSUED BY THE UNITED STATES PATENT OFFICE ON COMPRESSED 
AIR AND ITS APPLIANCES, FROM 1 875 TO JULY I,MC)OI. 



1875. 

Air Engine— Rider 167,568 

Air Engine — Eider 158,525 

Air Engine — Riley 165,027 

Air Compressor — Bailey 161,090 

Air Compressor — Corobbi & Bel- 
lini 159,075 

Air Brake — James 165,235 

Air Brake— Jones 166,386 

Air Brake— Ladd 165,337 

Air Brake— Moschcowitz 166,026 

Air Brake— Perrine .166,404 

Air Brake— Perrine 166,405 

Air Brake— Perrine 166,406 

Air Brake— Perrine 169,575 

Air Brake — Westinghouse 162,465 

Air Compressor — Reynolds 160,956 

Air Engine— Connolly 164,809 

1876. 

Air Engine— Sclinake 184,913 

Air Compressor — Crocker 176,931 

Air Compressor — Fulton 177,495 

Air Compressor— Hill .171,805 

Air Compressor — Laurence 172,751 

Air Compressor — Manz 176,795 

Air Brake— Chad wick 180,460 

Air Brake— Reniff 183,206 

Air Brake— Westinghouse 175,886 

Air Brake— Westinghouse 180,179 

Air Compressor — Sawtell. 183,596 

Air Compressor — Seal 174,860 

Air Compressor— Seal 182,333 

Air Compressor — Sturgeon 180,958 

Air Compressor— Tallman 176,096 

1877. 

Air Compressor— Babbitt. 198,067 

Air Compressor — Clayton. ._ 186,306 

Air Compressor — Garrison 186,336 

Air Brake— Green et al 198,015 

Air Brake— Stevens 191,261 

Air Compressor— Reynolds 187,906 

Air Compressor— Root 196,253 

Air Engine— Allen 193,631 

Air Engine— Davey 186,119 

Air Eno-ine— Hock & Martin 190,490 



1878. 

Air Engine— McKinley 206,597 

Air Engine— Rider 206,356 

Air Engine— Ward 198,827 

Air Compressor — Doremus 207,954 

Air Compressor— Dreyfus 200,901 

Air Compressor— Frizell 199,819 

Air Brake— Knapp 204,440 

Air Brake— Maxwell 207,126 

Air Brake— Newton 202,368 

Air Brake— Prince 204,914 

Air Brake— Raoul 203,647 

Air Compressor— Springer 211,062 

1879. 

Air Engine— Rider 220,309 

Air Engine— Sherrill 213,783 

Air Compressor — Clayton 222,014 

Air Compressor— Clayton 220,123 

Air Compressor— Gardner 221,802 

Air Compressor — Harvej^ 211,570 

Air Compressor — Jackson 218,029 

Air Compressor — Johnston 221,318 

Air Compressor — Moore 216,211 

Air Brake— Osgood 212,972 

Air Brake— Scbultz 220, 178 

Air Brake— Westinghouse 214,603 

Air Compressor — Pitchford 215,540 

Air Compressor — Spencer 214,465 

Air Compressor— Tatham 222,802 

Air Compressor— Thomas 217,834 

Air Compressor— Treat 221,126 

Air Engine— Eckart 216,563 

Air Engine — Hardie & James. . . .216,611 
Air Engine— Mathes 214,050 

1880. 

Air Engine— Presbrey 231,446 

Air Engine— Thuemmler 232,660 

Air Engine— Thuemmler 233,125 

Air Engine— Woodbury et al 228,712 

Air Engine— Woodbury et al. . . .228,713 
Air Engine — Woodbury et al. . . .228,714 

Air Engine — Woodbury et al 228,715 

Air Engine— Woodbury et al 228,716 

Air Engine— Woodbury et al 228,717 

Air Compressor— Bois 227,877 

Air Compressor— Bueil 234,751 

Air Compressor — Connor & Dods.232,939 



8o6 



COMPRESSED AIR AND ITS APPLICATIONS. 



Air Compressor — Eckart 224,081 

Air Compressor— Hill 229,821 

Air Compressor — Lawrence et al.. 226, 918 

Air Brake— Glenn 234,179 

Air Brake— Hall 231,311 

Air Brake— Loughridge 234,134 

Air Compressor — Parkinson 225,151 

Air Compressor— Pitchford 233,432 

Air Compressor — Richmann 229,468 

Air Compressor— Rix 235,296 

Air Compressor— Rix 235,816 

Air Compressor — Sergeant 233,881 

Air Compressor— Stockman 234,733 

Air Engine— Beaumont 232,438 

Air Engine— Ericsson 226,052 

Air Engine— Hill 229,821 

1881. 

Air Compressor— Alien 237,359 

Air Compressor — Allen 237,360 

Air Compressor — Boerner 239,310 

Air Compressor — Buell 246,657 

Air Compressor — Clayton 241,930 

Air Compressor — Cushier 236,992 

Air Compressor — Freeman 238,225 

Air Compressor — Fitzpatrick. . . .238,374 

Air Compressor— Hill 244,127 

Air Compressor— Hill. 244,128 

Air Compressor— Hill. 237,274 

Air Compressor— Hill 243,257 

Air Compressor — Hudson 241,984 

Air Compressor — Livingston 242, 008 

Air Compressor — Mayrhofer . . . .236,713 

Air Brake— Eames 241,323 

Air Brake— Eames 241,325 

Air Brake— Lorraine 246, 166 

Air Brake — Westinghouse 243,415 

Air Brake— Westinghouse 245,109 

Air Brake— Westinghouse 245,110 

Air Compressor — Quinn 236,455 

Air Compressor — Robinson & Ri- 
ser 248,218 

Air Engine — Lyman 236,954 

1882. 

Air Engine— Reynolds 262,119 

Air Compressor — Babcock 253,830 

Air Compressor— Baker 259,741 

Air Compressor — Beers 268,854 

Air Compressor— Bois 259,799 

Air Compressor — Bradley 254,915 

Air Compressor— Hill 261,606 

Air Compressor— Hill 261,605 

Air Compressor — Manning 256,232 

Air Compressor — Mayrhofer . . . .261,560 

Air Compressor — Monson 257,885 

Air Brake— Brockway et al 264,617 

Air Brake— Ford 266,684 

Air Brake— Hanscom 265,671 

Air Brake— Van Dusen 269,747 

Air Compressor — Overton 263,206 

Air Compressor— Overton 263,207 

Air Compressor — Rand 255,116 

Air Compressor — Reynolds 262,119 



Air Compressor — Sergeant 264,775 

Air Compressor— Smith . 269,730 

Air Compressor — Wang 255,222 

Air Compressor — Wang 255,901 

Air Compressor — Wang 262,157 

1883. 

Air Engine— Nash 278,257 

Air Engine — Wilcox 289,481 

Air Engine— Wilcox 289,482 

Air Compressor — Babcock 280,997 

Air Compressor — Babcock 287,358 

Air Compressor — Bennett 283,955 

Air Compressor — Bicknell 273,014 

Air Compressor— Cullingworth. .287,104 

Air Compressor — Fox 285,748 

Air Compressor — Freeman 290,764 

Air Compressor — Honigman 288,435 

Air Compressor — Lawler 272,711 

Air Brake (re -issue)— Ford. ...... 10,298 

Air Brake— Reilly .290,269 

Air Brake— Thayer et al .283,534 

Air Brake— Westinghouse 270,528 

Air Compressor— Moore 285,297 

Air Compressor — Reynolds 272,771 

Air Compressor — Sturgeon. .... .275,959 

Air Engine— Boy nton 289,967 

Air Engine— Cook 271,040 

Air Engine— Cook 272,656 

Air Engine — Eimecke 270,036 

Air Engine — McDonough 278,446 

1884. 

Air Engine— Robinson 309,163 

Air Engine— Stevens 305,114 

Air Engine— Wilcox (reissue)... 10,486 
Air Engine — Wilcox (re-issue).... 10,529 

Air Compressor— Allen 299,314 

Air Compressor— Bristin 302,978 

Air Compressor — Chichester 308,061 

Air Compressor— Cullen 307,442 

Air Compressor— Elders 301,348 

Air Compressor— Hill 292,814 

Air Compressor— Krutsch 302,206 

Air Brake— Dickson 306,140 

Air Brake— Flad 296, 546 

Air Brake— Flad 307,535 

Air Brake— Flad 307,536 

Air Brake— Green 309,845 

Air Brake— Magowan 293,481 

Air Brake— Mark 307,561 

Air Brake— Paradise 293,774 

Air Brake — Sjogren 300,401 

Air Brake— Sloan 307,344 

Air Brake— Willis 303,777 

Air Compressor — Moore 309,642 

Air Compressor — Norris 310,148 

Air Compressor— Pfanne 295,800 

Air Engine— Baldwin 292,400 

Air Engine— Bailsman .299,325 

Air Engine— Cramer 294,369 

Air Engine— Eteve & DeBraan. .309,835 

Air Engine— Graham .302,246 

Air En 2;ine— Leavitt 307, 312 

Air Engine— Maxim 293,185 



PATENTS. 



807 



Air 
Air 

Aii- 
Air 
Aii- 
Air 
Aii- 
Air 
Air 
Aii- 
Air 
Aii- 
Air 
Aii- 
Air 
Aii- 
Air 
Aii- 
Air 
Aii- 
Air 
Aii- 
Air 
Aii- 
Air 
Aii- 
Air 
Aii- 
Air 
Aii- 
Air 
Aii- 
Air 
Aii- 
Air 
Aii- 



Air 
Air 
Air 
Aii- 
Air 
Air 
Air 
Air 
Air 
Aii- 
Air 
Air 
Aii- 
Air 
Aii- 
Air 
Air 
Aii- 
Air 
Aii- 
Air 
Air 
Aii- 
Air 
Air 



1885. 

Engine— McTighe 321,739 

Engine— Pollock 316,656 

En o-me— Shilling 320,182 

En o-ine— Wilcox 332,312 

Engine— Wood 324,510 

Engine— Woodbury et al. . . .324.062 
Engine— Woodbury et al. . . .331,359 
Engine— Woodbury et al. . . .331,361 
Engine— Woodbury et al. . . .324,060 

Engine— Woodbury et al 324,061 

Engine— Woodbury et al 325,640 

Engine— Woodbury et al.. . .,327,748 

Compressor— Bolton 314,218 

Compressor — Corey 311,106 

Compressor— Erwiu 329,377 

Compressor — Erwin 333,208 

Compressor— Fox 321,206 

Compressor— Fox 321,207 

Compressor — Leavitt. '. 320,482 

Brake— Bass. 312,245 

Brake— Hanscom 326,646 

Brake— Hopper 321,971 

Brake— McKinney 311,196 

Brake— Sloan 327,027 

Brake— Sloan 330,164 

Compressor — Monson 328,598 

Engine— Bolton 314,218 

Engine — Bausman 313,646 

Engine— Coffield 322,796 

Engine— Colman 317,093 

Engine— Colman 317,628 

Engine— Corey 311,106 

Engine— Hanover 310,419 

Engine— Hurd 325,805 

En o-ine— Leavitt 321,985 

Engine— Limpus 329,914 

1886. 

Engine— Rider 345,450 

Engine— Rider 353,004 

Engine— Serdinko 335,388 

Compressor— Chichester 333,994 

Compressor — Cullingworth . . 355,002 

Compressor— Depp 333,613 

Compressor — Dow 341,099 

Compressor — Erwin 340,496 

Compressor— Fcvrot 336,224 

Compressor — Harrold 345,969 

Compressor— Hugentobler . . .342,798 

Compressor — Johnson 349,954 

Compressor — McLean 341,673 

Brake— Easton 354,014 

Brake— Goode 353,446 

Brake— Haberkorn. . . 335,446 

Brake— Hollerith 334,020 

Brake— Hollerith 334,021 

Brake— Hollerith 334,022 

Brake— Kneeland 351,383 

Brake— Melson 352,927 

Brake— Perkins 345,537 

Brake— Pickering 334,466 

Brake— Wisner 335, 094 

Compressor — Swartz 342,310 



Air Compressor— Thomas 337,209 

Air Engine — Babcock 334,152 

Air Engine — Babcock 334,153 

Air Engine— Babcock 334,154 

Air Engine — Lachmann 333,644 

1887. 

Air Engine— McKinley. 356,146 

Air Engine— McKinley 356,147 

Air Engine— Philpott 359,282 

Air Engine— Tasker 364,451 

Air Compressor— Chichester 370,376 

Air Compressor — Cummings 363,509 

Air Brake— Bass 358,142 

Air Brake— Carpenter 359,953 

Air Brake— Hanscom 369,057 

Air Brake— Westinghouse 360,070 

Air Compressor — Strange 373,419 

Air Engine — Baldwin & Bradford 

355,633 
Air Engine— Close 366,204 

1888. 

Air Engine— Rider 393,663 

Air Engine —Rider 393,723 

Air Engine— Winched 381,313 

Air Compressor — Chamberlain. . .376,141 
Air Compressor — Cullingworth. .377,481 

Air Compressor: — Dean 380,195 

Air Compressor— Erwin 382,760 

Air Compressor — Forster ... .375,929 

Air Compressor — Forster 376,589 

Air Compressor— Forster 384,356 

Air Compressor— Hunter 392,611 

Air Compressor — Keenan 384,529 

Air Compressor— McKim 375,761 

Air Brake— Andrews 385,224 

Air Brake— Boluss 382,749 

Air Brake— Carpenter 378,657 

Air Brake— Dixon . . .382,031 

Air Brake— Dixon 389,643 

Air Brake— Guels 384,686 

Air Brake— Guels 384,687 

Air Brake— Harvey 378,365 

Air Brake— Lansberg 386,640 

Air Brake— Lansberg 392,872 

Air Brake— Lehy 381,392 

Air Brake— Lewis. 383,819 

Air Brake— Park 385,198 

Air Brake— Park 393,784 

Air Brake— Solano 376,970 

Air Brake— Solano 378,628 

Air Brake— Solano 382,667 

Air Brake— Solano 387,018 

Air Brake— Williams 393, 950 

Air Compressor — Nosbaume 393,172 

Air Compressor— Pitt 386,028 

Air Compressor — Reynolds 378,336 

Air Engine— Bair 389,045 

Air En o-ine— Clark 386,454 

Air Engine— Genty 387,063 

1889. 

Air Engine— Schmid & Beckfeld.403,294 
Air Engine— Stevens 414,173 



8o8 



COMPRESSED AIR AND ITS APPLICATIONS. 



Air 
Air 
Air 
Air 
Aii- 
Air 
Air 
Air 
Aii- 
Air 
Aii- 
Air 
Aii- 
Air 
Aii- 
Air 
Aii- 
Air 
Aii- 
Air 
Aii- 
Air 
Air 
Air 
Air 
Air 
Aii- 
Air 
Air 
Aii- 
Air 
Aii- 
Air 
Air 
Aii- 
Air 
Aii- 
Air 
Aii- 



Air 
Aii- 
Air 
Air 
Aii- 
Air 
Aii- 
Air 
Aii- 
Air 
Air 
Air 
Aii- 
Air 
Aii- 
Air 
Air 
Aii- 
Air 
Aii- 
Air 
Aii- 
Air 
Air 



Engine— Woodbury et al 404,237 

Engine— Wright 408,784 

Compressor — Cummings 412,474 

Compressor — Davey 409, 773 

Compressor — Fitzpatrick 402,517 

Compressor — Funk 417,717 

Compressor — Guthrie 417,482 

Brake— Boluss 414,138 

Brake— Boluss 398,310 

Brake— Collins 400,638 

Brake— Collins. 400,639 

Brake— Dixon 402,418 

Brake— Dixon 412,168 

Brake— Dixon 418,506 

Brake— Daellenbach 415,162 

Brake— Haberkom .398,829 

Brake— Haberkorn 413,253 

Brake— Holleman 405,705 

Brake— Lansberg 415,513 

Brake — Lansberg 415,514 

Brake— Lansberg 415,515 

Brake — Lansberg 415,516 

Brake — Lansberg .415,517 

Brake— Lapish 399,420 

Brake— Lewis 410,288 

Brake— Marsh 396,284 

Brake— Massey 414,717 

Brake— Maxwell 405,968 

Brake— Norris 413,205 

Brake— Park 407,445 

Brake— Pitehard 410,922 

Brake— Pitchard et al 399,158 

Brake— Pilchard et al 399,157 

Brake— Rymer 416,953 

Brake— Solano 405,855 

Brake— Solano 406,006 

Compressor — Sergeant 415,822 

Engine— Baldwin 404,818 

Engine— Humes 400,850 

1890. 

Engine— Brock 434,422 

Engine— Eastman 443,641 

Engine— Ericsson 431,792 

Engine— Harder 438,251 

Engine— Metzing 441,103 

Engine— McCalia 420,824 

Engine— McTighe , 429,281 

Engine— McTighe 429,282 

Enoine— McTighe 429,283 

Eno-ine— Rogers 427,911 

Engine— Schmid & Beckfeld. 421,525 

Engine— Vivian 437.320 

Compressor — Eloheimo 435,034 

Brake— Boluss 435,791 

Brake— Burbank et al 428,299 

Brake— Daellenbach 442,019 

Brake (re-issue)— Quels 11,070 

Brake— Guillemet 437,300 

Brake— Harris 442,621 

Brake — Hogan 433,127 

Brake— Hosjan 433,594 

Brake— Hogan 433.595 

Brake— Hopper 430,024 

Brake— Lansberg 439.528 



Air Brake— Maher 433,737 

Air Brake— Martin 437,218 

Air Brake— Roberts 433,040 

Air Brake— Robinson 437,800 

Air Brake— Stewart 420,121 

Air Brake— Schroyer 426,144 

Air Brake— Walker 438,038 

Air Brake — Westinghouse 421,641 

Air Brake— Williams 441,526 

Air Brake— Williams 431,303 

Air Brake— Williams 431,790 

Air Brake (re-issue)— Williams. . . 11,124 

Air Brake— Williams 431,304 

Air Compressor— Hill 439,876 

Air Compressor — Massey 433,951 

Air Compressor — Rand & Halsey .421,611 

1891. 

Air Engine— Benster 463,092 

Air Engine — Bergman 463,025 

Air Engine— Chapman 447,066 

Air Engine— Griswold 455,201 

Air Engine— Hall 457,272 

Air Engine— Hall . . .' .457,273 

Air Engine — Jefferson. . ..... .464,364 

Air Engine — Robinson 445,904 

Air Engine — Rusk 458,070 

Air Compressor — Clark 453, 374 

Air Brake— Barnes et al 462,193 

Air Brake (re-issue)— Bayley. .. . 11,145 

Air Brake— Bothwell 456,247 

Air Brake— Beery 452,334 

Air Brake— Dock! 462,966 

Air Brake — Hogan 447,731 

Air Brake— Hopper 458,626 

Air Brake— James 447,236 

Air Brake— James , 461,243 

Air Brake— Lansberg 445,899 

Air Brake— Marshall 456,199 

Air Brake — Massey 451,409 

Air Brake— Massey 447,783 

Air Brake — Riggs 457.215 

Air Brake— Slater. 452,942 

Air Brake— Waite 463,085 

Air Brake— Westinghouse 448,827 

Air Brake — Westinghouse et al.. .461,779 

Air Brake— Wisner. 446.908 

Air Compressor — Hill 448,859 

Air Compressor — Hill 452,132 

Air Compressor — Hill 454,590 

Air Compressor— Hill 463,386 

Air Compressor — Nordberg 458.975 

Air Compressor — Phillips 452,283 

Air Compressor — Richards 462,776 

Air Compressor— Richmann 459,527 

Air Compressor — Richmann 462,453 

Air Compressor — Sergeant 447,910 

Air Compressor — Sergeant 456,165 

1892. 

Air Compressor — Avery 482,775 

Air Compressor — Beck 476,723 

Air Compressor — Dillenburg . . . .481,850 

Air Compressor— Dunn 473,302 

Air Compressor— Farrell 479,260 



PATENTS. 



809 



Air 
Aii- 
Air 
Aii- 
Air 
Aii- 
Air 
Aii- 
Air 
Aii- 
Air 
Aii- 
Air 
Aii- 
Air 
Aii- 
Air 
Air 
Aii- 
Air 
Aii- 
Air 
Aii- 
Air 
Air 
Aii- 
Air 
Aii- 
Air 
Aii- 
Air 
Aii- 
Air 



Aii- 
Air 
Air 
Aii- 
Air 
Air 
Aii- 
Air 
Air 
Aii- 
Air 
Aii- 
Air 
Aii- 
Air 
Aii- 
Air 
Air 
Aii- 
Air 
Aii- 
Air 
Aii- 
Air 
Aii- 
Air 
Air 



Compressor — Fasoklt 481,527 

Compressor — Guillemet 482,040 

Compressor — Haines 470,934 

Compressor— Haines 480,193 

Compressor — Hanford 474,296 

Compressor — Hanston & Bur- 
dan. . 471,766 

Brake— Beery 485,365 

Brake— Coates 467,920 

Brake— Coates 467,921 

Brake— Corporau. . 483,802 

Brake— Carpenter 479,736 

Brake— Duval , 486.703 

Brake— Dunn 473,302 

Brake— Falirney 485,182 

Brake— Guillemet 482,040 

Brake— Hannev 476,880 

Brake— Harris'. .472,190 

Brake— Hayden 481,651 

Brake— Ho'gan 473,839 

Brake— Hogan 482,058 

Brake— Knudsen 468,387 

Brake— McNnlta 471,801 

Brake— Marble 484,034 

Brake— Mills 476,546 

Brake— Pelton 482,382 

Brake— Shortt 469,176 

Brake— Silcock 468,701 

Compressor — Henderson tfe 

Schultz 475,111 

Compressor — Hutchinson. . . .581,143 

Compressor — O'Brien 477,381 

Compressor — Perry 485,881 

Compressor — Sherman 475,251' 

Compressor — Teal 474,034 

1893. 

Engine— Durand 497,048 

Engine— Field 506,486 

Eno-ine— Hauser & Whittaker.489,148 

En o-i ne— Martin 500,340 

Engine— Muselman 502,860 

Engine— Schon 508,990 

Engine— Smith 491,859 

Compressor — De Laval 511,086 

Compressor— Fogg 493,263 

Compressor— Gustaf son 509,220 

Brake— Barber 494,772 

Brake— Dean 511,071 

Brake— Duval 510,635 

Brake— Duval 510,870 

Brake— Dunn 489,527 

Brake— Erbody 510,594 

Brake— Hayden 509,898 

Brake— Higgins 503,083 

Brake— Hinckley 508,421 

Brake— Key wood 500,910 

Brake— Massey 501,016 

Brake — Masterman 504,227 

Brake— Parke et al 506, 185 

Brake— Pinkston 501,359 

Brake— Pool et al 499,582 

Brake— Shallenberger 506,739 

Brake— Sennett et al 489,763 

Compressor — Knoche 508,225 



Air Compressor— Perry 498,989 

Air Compressor — Quast 501,046 

Air Compressor — Schutzinger. . ..508,150 
Air Compressor— Walker 491,232 

1894. 

Air Engine— Depp 521,762 

Air Engine— Rogers 511,969 

Air Engine— Stewart 519,977 

Air Compressor — Babcock 523,064 

Air Compressor — Birner & Mes- 
sing 520,405 

Air Compressor — Brotherhood. . .515,282 

Air Compressor — Champ 513,556 

Air Compressor — Champ 515,516 

Air Compressor— Champ 523,830 

Air Compressor — Flood 519,383 

Air Compressor — Griffiths et al. . .530,335 

Air Brake— Bayley 528,712 

Air Brake— Brown 520,391 

Air Brake— Barbridge et al 526,178 

Air Brake— Bishop . . 581,584 

Air Brake— Clark 522,825 

Air Brake— Clifton 531,100 

Air Brake— Edwards 527,838 

Air Brake— Eldridge 527,327 

Air Brake— Fox 530,937 

Air Brake— Fox 530,938 

Air Brake— Fox 530,939 

Air Brake— Haberkoru 531,181 

Air Brake— Harris 515,220 

Air Brake— Harris 516,202 

Air Brake— Hunt 529,270 

Air Brake— James 524,990 

Air Brake -Jeffries 513,267 

Air Brake— Knudsen 525,686 

Air Brake — Lansberg 516,936 

Air Brake — Lencke 517,955 

Air Brake— Lencke et al 517,954 

Air Brake— McCarty 529,290 

Air Brake— Mable 526,189 

Air Brake— Mills 537,784 

Air Brake— O'Hara 519,681 

Air Brake— Rothschild 515,616 

Air Brake— Rothschild 515,617 

Air Brake— Richardson. 513,145 

Air Brake— Sehenck 524,073 

Air Brake— Sehenck '. . . .531,137 

Air Brake— Shortt 530,904 

Air Brake— Stewart 517,250 

Air Brake— Vorhees 524,050 

Air Brake— Vorhees 525,876 

Air Brake— Willson 516,692 

Air Compressor— North 527,248 

Air Compressor — Schutz-Hender- 

son 517,628 

Air Compressor — Sergeant 514,839 

Air Compressor— Sergeant 530,662 

1895. 

Air Engine — Anderson 537,517 

Air Engine — Bramwell 543,462 

Air Engine— Denney 538,068 

Air Engine — Fletcher & Hug- 

gings 547,718 



8io 



COMPRESSED AIR AND ITS APPLICATIONS. 



Air Engine— Parsons 549,741 

Air Engine— Sherman 535,602 

Air Compressor — Blake 534,192 

Air Compressor — Champ 544,456 

Air Compressor — Champ 544,457 

Air Compressor — Champ 544,458 

Air Compressor— Champ 544,459 

Air Compressor — Champ 547,768 

Air Compressor — Chaquette .548,800 

Air Compressor — Clayton 534,814 

Air Compressor — Duffy 547,338 

Air Compressor — Durand 550,163 

Air Compressor— Griffiths et al. ..547,882 

Air Brake— Clarke 549,703 

Air Brake— Con ness 540,539 

Air Brake— Christensen 534,813 

Air Brake— Dunn 546,510 

Air Brake— French 533,286 

Air Brake— Harris 544,253 

Air Brake— Harris 547,253 

Air Brake— Hogan 546,448 

Air Brake— Hogan 546,449 

Air Brake — Hogan 551,440 

Air Brake— Hogan 551,767 

Air Brake— Humbert et al 539,430 

Air Brake— Hunt 545,295 

Air Brake— Jeffries 550,346 

Air Brake— Massey 535,844 

Air Brake— Massey 537,057 

Air Brake— Schenck 532,914 

Air Brake— Sennett 536.000 

Air Brake— Shortt 538,547 

Air Brake— Shortt 538,551 

Air Brake— Shortt 538,544 

Air Brake— Shortt 538,549 

Air Brake— Shortt et al 538,546 

Air Brake— Steedman 542,948 

Air Brake — Thompson 545,749 

Air Brake— Tower et al 538,299 

Air Brake— Trott 536,002 

Air Brake— Wessels et al 548,335 

Air Brake— Wheeler 546,835 

Air Brake— White 538,002 

Air Compressor — Kalthoff 551,549 

Air Compressor — Keenan 547,519 

Air Compressor — Lowe & Guyser.534,399 

Air Compressor — Moyer 541,979 

Air Compressor — Noack 550,352 

Air Compressor — Pedrick 544,548 

Air Compressor — Stambaugh 548,399 

Air Compressor— Taylor 543,410 

Air Compressor — Taylor 543,411 

Air Compressor — Taylor. 543,412 

1896. 

Air Engine — Bercher 558,475 

Air Engine— Coon 555,929 

Air Engine— Good 560,707 

Air Engine— Good & Marichal. . .558,944 
Air Engine — Mihsbach & Groe- 

schell 566,785 

Air Engine— AValling 565,191 

Air Compressor — Champ 570,540 

Air Compressor — Chaquette 565,429 

Air Compressor — Clark 558,041 



Air Compressor — Du Faur 561,160 

Air Compressor— Elliott 568,433 

Air Compressor — Githens 563,477 

Air Compressor — Guyser 560,987 

Air Brake— Beemer 564,863 

Air Brake— Brookmire 558,670 

Air Brake— Custer 553,481 

Air Brake— Custer 553,482 

Air Brake — Dunn 553,517 

Air Brake— Dunn 567,024 

Air Brake— Fernley et al 553,498 

Air Brake— Genett 556,815 

Air Brake— Glass 569,915 

Air Brake— Graebing 569,823 

Air Brake— Guillemet 571,115 

Air Brake— Guillemet 571,116 

Air Brake— Hall 574,062 

Air Brake— Harris 571,662 

Air Brake- Herder 558, 174 

Air Brake— Herbert 572,009 

Air Brake— High 555,809 

Air Brake— Howe et al 567,476 

Air Brake— June 570,483 

Air Brake— Lee 557,511 

Air Brake— Lee 557,512 

Air Brake— Lee 557,513 

Air Brake— Lee 557,514 

Air Brake— Lee 557,515 

Air Brake— Lindsev 561,596 

Air Brake— MaMe." 572,553 

Air Brake— Marshall 560,730 

Air Brake— Noyes 553,565 

Air Brake— Noyes 564,389 

Air Brake— Noyes 571,095 

Air Brake— Noyes 571,786 

Air Brake— Omick 563,612 

Air Brake— Park 561,811 

Air Brake— Reyburn 568,923 

Air Brake— Rogers et al 553,294 

Air Brake— Thompson 571,708 

Air Brake— Walker et al 569,258 

Air Brake— Westinghouse 557,464 

Air Brake— Willets 561,301 

Air Brake— Zenke 571,736 

Air Compressor— Hill 571,971 

Air Compressor — Liming 569,929 

Air Compressor— Merritt 562,475 

Air Compressor — Nichols 555,178 

Air Compressor — Noyes 563,794 

Air Compressor- — Pendleton 561, 126 

Air Compressor— Reynolds 572,377 

Air Compressor— Roberts 572,314 

Air Compressor — Sergeant 568,804 

Air Compressor — Shaw 552,590 

Air Compressor — Smith 572, 383 

Air Compressor — Underwood. , . .558,125 

1897. 

Motor Car— R. Hardie 584,146 

Air Compressor— I. T. Dyer 585,090 

Pneumatic Despatch— B. C. Bach- 

eller 585,498 

Air Spray— John Black 585,503 

Air Brake— E. A. Trapp. 585,927 



1 1 



Compressor and Cooler — John 

Flindall 585,955 

Air Compressor— W. H. Knight.. 586, 100 

Air Motor— J. H. Hoadley 586,127 

Pneumatic Sole— Julia F. Bas- 

com 586,155 

Air Compressor — Alfred Shed- 
lock 586,669 

Pneumatic Press — P. C. Blais- 

dell 586,946 

Air Compressor — I. H. Spencer. .588,296 
Hot- Air Motor— W. Trewhella. ..588,509 
Air Compressor— E. C. Nichols. .589,190 

Water Elevator— John Hass 588,825 

Pneumatic Conveyor — A. P. Hes- 

lop 588,908 

Valve— James Clayton 587,704 

Air Pump— H. S. Bills 587,638 

Railwav Switch — Johnson & Mc- 

Keithen ...590,153 

Straw Stacker— L. D. Parmley... 589,853 
Pneumatic Motive Power— L. H. 

Meyer 590,686 

Pneumatic Tool— F. E. Hartham. 590,661 
Air or Gas Compressor— S. S. 

Miles 591,137 

Pneumatic Drill— J. H. Manning. 591, 284 
Pneumatic Motor— G. W. Smith.. 591, 018 
Water-Elevator— P. S. A. Bickel. 591,029 
Pneumatic Hammer — C. H. John- 
son 592.116 

Air Compressor— E. Hill 593,049 

Pneumatic Painting Apparatus — 

A. Fisher 593,013 

Pneumatic Water-Raising Device 

— E. Pitcher 593,431 

Pneumatic Motor — F. W. Hedge- 
land 593,655 

Pneumatic Motor— T. P. Brown.. 594, 891 
Air-Controlling Device — A. 

Roesch 595, 654 

Pneumatic Conveyor — S. H. 

Jones 596,211 

Dry Kiln— Franklin Kirk 596,212 

Pneumatic Stacker — G.W.Quinn.596,307 
Drying Ap paratus — McClatchey 

&Krum " 596,175 

Pneumatic Despatch Tube— C. F. 

Pike 595,890 

Air Pump or Compressor — L. R. 

Alberger 595,429 

Air Engine — Anderson & Ericks- 

son 579, 670 

Air Engine — Barbour & Hansen. .591,584 

Air Engine— Berry 582,257 

Air Engine— Bole 592,688 

Air Engine— Gibbs 592,246 

Air Engine— Goth 580,600 

Air Engine— Parke 594,901 

Air Engine — Roediger 579,654 

Air Engine — Weimer 577,568 

Air Compressor — Crabtree 594,524 

Air Compressor — Griffiths et al. . .576,364 

Air Brake— Bovden 583,278 

Air Brake— Boy den 583,279 



Air Brake— Buekpitt. 589,957 

Air Brake— Bragg et al 593,531 

Air Brake— Bentley 574,656 

Air Brake — Conness 587,519 

Air Brake — Corrington. . . 594,464 

Air Brake — Dunn 577,425 

Air Brake— Fish 593,996 

Air Brake— Gunckel 582,391 

Air Brake — Hogan 574,866 

Air Brake— Hunt 581,912 

Air Brake — Mcintosh 589,265 

Air Brake — Nellis et al 594,033 

Air Brake— Omick 588,913 

Air Brake— Red fern 584,705 

Air Brake — Shearwood 574,498 

Air Brake — Shortridge 578,168 

Air Brake — Westinghonse et al.. .592,461 

Air Brake— Winters 594,228 

Air Compressor — Perine 580,714 

Air Compressor— Sergeant 579,775 

Air Compressor — Toennes 576,920 

Air or Gas Compressor — J. Crab- 
tree 594,524 

1898. 

Air Lift Pump— W. L. Saunders. 567, 023 
Compressed - Air Apparatus — J. 

Mclntyre 596,822 

Drier— K. S. Blanchard 596,470 

Grain Drier— W. E. Ellis 596,655 

Refrigerator— J. H. Barrett 596,967 

Air Compressor— T. H. Roberts.. 597, 223 
Lumber Drier— H. J. Morton. . . .597,543 

Air Valve— S. C. Arnold 597,666 

Air Brake— H. F. Noyes 599,348 

Air Compressor— J. H. Hoadley.. 598, 149 
Governor Valve, Compressor — 

Christensen 598,283 

Pneumatic Spring— W. Kowaleff.598,102 
Air Disc-Brake— M. E. Campany. 598,766 
Air Cleaning, Cooling Device — 

McCreery 599,080 

Pneumatic Conveyor — S. C. Da- 
vidson 599,055 

Pneumatic Spring — E. L. Egger.598,982 
Pneumatic Stacker— G.W.Wood . 599,279 
Street-Car Air Brake— C.A.Gray. 599,421 

Drier— A. S. Livengood 599,509 

Fruit Drier— Steevens & Steevens 

599,647 

Air Brake— Noyes 599,349 

Air Compressor — P. Cramer . . . .600,258 
Air Compressor (re-issue) — F. M. 

Graham 11,654 

Compressor— J. Stumpf 600,626 

Hot-Air Compressor — Anderson 

& Ericksson 601,031 

Air Brake— W. O. Gunckel 601,253 

Air-Brake Valve— W.O. Gunckel .601,252 
Pneumatic Hub — W. C. Kone- 

man 599,907 

Liquid Distribution — F. M. Gris- 

wold 599,702 

Air Brake— Catlett 598,814 

Air Brake— Gunckel 601,253 



812 



COMPRESSED AIR AND ITS APPLICATIONS. 



Air Brake— Hamar et al 600,641 

Air Brake— Kholodowski 600,537 

Air Brake— Olin 598,678 

Air Brake— Perkins 598,887 

Air Brake— Pettengell 597,220 

Air Brake— Wands ■ 604,244 

Air Compressor— H. C. Sergeant. 602, 877 
Compressed-Air H a m m e r — J. 

Schmidt 602,198 

Valve, Air Compressor — F. Rich- 
ards 602,473 

H y d r a u 1 i c Air Pump — E. IT. 

Weatherhead 603,242 

PI ydraulic Air Compressor — 

W. F. Stark 602,247 

Air Brake— J. J. Nef 602,094 

Air Valve— E. A. Rix 602,170 

Hot- Air Furnace— J. T. Warren.. 601, 822 

Air Distributor— J. Jauch 603,105 

Pneumatic Despatch Tube— H. 

Clay 603,174 

Pneumatic Organ— M. Clark. .. .603,127 
Governor Air Compressor — C. 

Cummings 603,425 

Pneumatic Elevator— J. B. Schu- 

man 603,925 

Pneumatic Despatch — Mathias. ..604,405 

Air Brake— W. O. Gunckel 604,612 

Compressed Air Engine— L.- T. 

Gibbs 604,745 

Air Compressor — O. H. Bring- 

ham 604,717 

Air Compressor— E. Bottini 604,962 

Air Brake— W. H. Clowrv 605,394 

Hot- Air Furnace— T. G. Neal. ...605,329 

Air Brake— H. S. Park 605,904 

Air Brake— H. S. Park 605,905 

Pneumatic Motor— F. W. Hedge- 
land 605,876 

Air Compressor— F. Richards. .. .606,428 
H y d r a u 1 i c Air Compressor — 

Noack 606,732 

Hydraulic Air Compressor— 

Noack 606,733 

Air Brake— William Hirst 607,371 

Air Brake— M. Carrington 606,708 

Air Brake— L. F. Gmllemet 606,712 

Hot-Air Furnace— H. L. Win- 

gert 606,752 

Valve-Gear, Air Compressor — Se- 

derholm 607,195 

Hot- Air Furnace— J. T. & J. K. 

Brien 607,793 

Gas Power Process — E. N. Dick- 

erson 607,655 

Air Brake— C. L. Ansley 608,095 

Air Brake— Murray Corrington. .608,030 
Air Compressor— C. N. Dutton. .609,087 
Air Compressor— C. N. Dutton. .609,088 
Air Compressor — Heston & Har- 

vison 608,964 

Air Brake— F. L. Guillemet 608,599 

K Air Brake— F. L. Guillemet 608,600 

Air Brake— H. S. Parke 608,621 

Air-Brake— J. J. Nef 609,041 



Air Brake— J. J. Nef 609,042 

Pneumatic Despatch Tube— S. R. 

Gayton 610,528 

Air-Compressor Inlet-Valve— J. 

G. Leyner 610,608 

Tide-Water Air Compressor — 

Beckers 610,790 

Pneumatic Motor — F. W". Hedge- 
land 611,629 

Locomotive Air Brake— W. P. 

Alter 612,149 

Automatic Air Brake— McLaugh- 
lin 612,778 

Air Brake— W. T. Hamar 613,142 

Air Compressor Governo r — 

Libby 613,692 

Air Agitator— E. F. Porter 614,275 

Air Engine— M. Schmidt. .... . .614,992 

Air Brake— J. F. Voorhees 615,326 

Pneumatic Dry Dock — C. N. Dut- 
ton 615,440 

Air Compressor— W. H. Barr. . . .615,668 
Pneumatic Gas Lighter — E. 

Knapp 615,717 

Air Brake— M. Corrington 616,288 

1899. 

Hydraulic Air Compressor — Ster- 

zing 618,242 

Hydraulic Air Compressor — Tay- 
lor 618,243 

Air Brake— E. A. Hauerwas. . . .'.618,204 
Air Purifier— W. S. Whitney. . . .616,997 

Air Moistener— W. H. Prinz 618,615 

Air Compressor — Lowell & 

Brown 618,959 

Air Brake— R. E. Wynn 619,381 

Air Heater— J. Higginbottom. .. .619,483 

Air, Gas Engine— Eisenhuth 620,554 

Air Brake— Ansley & Topham. . .621,779 
Liquefying Air — Ostergren & 

Burger 621,536 

Liquefying Gas — Ostergren & 

Burger 621,537 

Air Compressor— H. E. Anderson. 620,822 
Aerating Water in Bottles— H. V. 

R. Reed 620,963 

Air Valve— J. H. K. McCollum. .621,841 
Air-Supplying Apparatus — F. A. 

Baynes 620,830 

Air Brake Safety Attachment — 

A. C. Rumble 624,103 

Air Compressor— F. W. Ensign.. 624, 002 
Pneumatic Despatch — E. A. For- 

dyce 624,201 

Pneumatic Carrier — E. A. For- 

dyce 624,202 

Pneumatic D e s p a t c h — B. C. 

Batcheller 623,970 

Pneumatic Despatch— B. C. 

Batcheller 623,971 

Carrier— B. C. Batcheller 623,972 

Carrier Receiver— B. C. Batchel- 
ler 623,973 



PATENTS. 



13 



Pneumatic Transmission — Batch - 



.60:]. 9(38 



Pneumatic Transmission — Batch - 

eller 623.969 

Air Compressor— A. Eoesch 634,009 

Hydraulic Air Compressor — J. 

Liming 624,830 

Gas Engine— W. II. & J. Butler- 
worth 624,750 

Compound Air Compressor — 

Wallick 624,998 

Valve for Air Motors — J. Craig, 

Jr 625,324 

Reducing Valve — J. Craig, Jr... .625,325 
Liquefying Gases— J. E. John- 
son 627,696 

Air Compressor and Cooler — R. 

Berg 626,883 

Pneumatic Dispatch Carrier — 

Fordyce 627.181 

Pneumatic Organ— M. Clark 626,320 

Compression Controller — F. G. 

Hobart 627,850 

Air Cooler— J. McCreery 626,390 

Atomizer— Pv. Morrill 628,251 

P n e 11 m a t i c Carpet-Sweeper — 

Westman 628,505 

Water Elevator— F. Hayes 628,318 

Air-Brake Hose Coupling — J. 

Caldwell 629,657 

Air Brake— E. Bartholomew 629,708 

Triple Valve for Air Brakes— W. 

B. Mann 630,379 

Engine for Air Pumps — W. B. 

"Mann 630,380 

Air Brakes— W. B. Mann 630,381 

Air Compressor— R. L. Dunn. .. .630,495 
Air Compressor — C. O. Sobinski. . 630, 525 
Pneumatic Propulsion — Walker . .630,821 

Air Controller— S. H. Short 630,938 

Air Cooler— J. McGreery 631,377 

Pneumatic Hammer — C. K. Pick- 
les 631,435 

Air Compressor — C. F. DuBois. .631,701 
Compressed Air Pump — T. C. 

Wristen 631,732 

Air Purifier— Fowler & Harpole.,631,868 
Air Compressor— P. H. Montague . 631 , 994 

Air Drill— A. P. Schmucker 633,661 

Pneumatic Organ— M. Clark 632,698 

Pneumatic Despatch— Batcheller. 632, 690 
Pneumatic Signal for Trains — C. 

Guiland 632,813 

Track-Sanding Device — J. H. 

Handon 633,193 

Track-Sanding Apparatus — J. H. 

Handon 633,194 

Valve for Pneumatic Tools — J. 

Boyer 633,355 

Valve * Controller— Schoeffel & 

Aylward 632,207 

Combustion Motor— R. Mewes. . .633,878 
Pneumatic Pipe Orga n — 

Schmelzeis 633,735 

Pneumatic Insole — A. Korwan. ..632,529 



Pneumatic Carpet Renovator — 

Thurman 634,042 

Air Feeder for Furnaces — J. How- 
den 634,348 

Air Compressor— P. Brotherhood. 634,389 

Air Brake— C. K Dutton 634,723 

Air Compressor — S. Broichgaus.. 635,419 
Pneumatic Despatch— Fordyce . . 635,434 
Hydraulic Air Pump— Haber- 

mann 635,478 

Air Compressor — J. P. Simmons. 635,516 
Air Compressor — J. P. Simmons. 635,517 

Air Valve— W. J. Cole 635.661 

Portable Air Pump— A. B. Diss.. 635, 674 
Automatic Air Brake— Clarke. . ..635,095 
Air Compressor— G. W. Tolle . . .636,013 
Air Heater— Waterman & Mori- 
son 636,090 

Air Purifying Apparatus— E. 

Gates 636,256 

Sand Blast— J. M. Newhouse 636,279 

Tire Inflater— J. F. Wilson 636,308 

PneumaticValve— H.Leineweber.636,343 
Cotton-seed Conveyor — J. T. 

Moore ' 636,414 

Cow-Milker— K H. Norby 636,446 

Compressor, Ice M a c li i ne s— 

Sharpneck 636,459 

Sand-Blast Machine— G. S. Slo- 

cum 636,460 

Air Compressor— S. A. Donnelly .636,643 

Air Purifier— J. C. Fleming 636,651 

Cotton-Handler— D. C. Jones. .. .636,670 
Time Valve— F. L. Dodgson. . . .636,770 
Air-Brake Hose-Coupling— Park- 
inson 637,021 

Pneumatic Rocker — Anderson & 

Anderson 637,065 

Hydraulic Air Compressor — L. E. 

Mitchell 637,144 

Pump for Compressing Air or 

Gas— H. E. Ludwig 637,516 

Air Compression — Pettee & Mc- 

Cutchan 637,659 

Air Motor— Pettee & McCutchan.637,660 
Air Compression— Pettee & Mc- 

Cutchan 637,661 

Air Supplier for Diving — F. A. 

Hensley 638,392 

Pneumatic Despatch — C. F. Bo- 

dinus 638,409 

Air Compressor — J. H. Hopps. . .638,460 
Pneumatic ' Ram — A. L. Hum- 
phrey 638,928 

Air Pyrometer — Uehling & Stein- 

bart 639,317 

Mercurial Air Pump — H. S. Max- 
im ...639,593 

1900. 

Air Propeller— A. Duffner, Jr. . ..640,184 

Air Drier— A. T. Perkins 640,318 

Air Drier— A. T. Perkins 640,320 

Pneumatic Tube— S. F. Jones. ...640,386 



8i4 



COMPRESSED AIR AND ITS APPLICATIONS. 



Air and Gas Engine— F. W. Eisen- 

liuth 640,890 

Air Ejector — G. Quanonne 640,946 

Air-Compressing Engine — E. A. 

Rix 640,949 

Air Pump— C. E. Scribner 641,409 

Pneumatic Despatch Tube— C. A. 

Gray 641,384 

Air-Lock Caisson — R. S. Gillespie. 641,505 
Air Compressor — W. D. Hooker.. 648, 135 

Reheater— T. A. Eclison 643,764 

Hydraulic Air Compressor — How- 
ard 643,962 

Marine Air Compressor— J. F. 

Place 644,093 

Electric Controller— Cbristensen.. 644, 128 
Liquid Air Storage — Ostergren . .644,259 

Air Meter— S. L. Terry 644,340 

Pneumatic Water Supply — Kins- 
man * 644,711 

Pneumatic Separator — C.H. Lane. 645, 962 

Air Compressor — McKinnon 646,030 

Air Compressor — McKinnon 646,031 

Air-Pipe Coupling— Spurlock. ...646,240 
Compressed-Air Motor — B. P. 

Ryder 646,318 

Pneumatic Hoist— H. A. Pedrick. 64 6,458 
Liquid-Air Vessel— J. P. Place... 646, 459 
Air Lift Pump— G. H. Evans. .. .646,640 

Sand Blast— W. H. King 646,740 

Air Belt-Shipper— J. Woodberry . 646, 892 
Pneumatic Spring — J. C. Ander- 
son 647,246 

Liquid-Air Bottle— H. Karrodi. ..647,002 

Pneumatic Drill— J. A. Hoff 647,265 

Pneumatic Tool— J. Keller 647,415 

Pneumatic Rammer — J. Keller. .647,416 
Pneumatic Drill— E. C. Meissner. 647,455 
Liquefaction of Air— O. P. Oster- 
gren 647,514 

Pneumatic Carrier— B. C. Batch- 

eller 648,375 

Air Refrigerating— J. D. Moran .648,422 
Locomotive Track-Sander — C. A. 

Pratte ...648,709 

Pneumatic Despatch Carrier— J. 

T. Cowley 648,853 

Signal— J. H.' McCarthy 649,523 

Heater for Air Motors— J. Craig, 

Jr 650,525 

Pneumatic Propeller — J. P. 

Hickey 650,535 

Explosive Liquid- Air Engine — J. 

C. Anderson 651,741 

Dry-Air Apparatus— J. Gayley. 652,178 
Air-Drying Process — J. Gayley. .652,179 
Pneumatic Tube — W. A. Hough- 

taling 652,270 

Air Cooler— J. McCreery 652,463 

Pneumatic Store Service— H. W. 

Forslund 652,537 

Air Pump— C. M. Hobby 652,559 

Air Compressor— H. C. Sergeant, 647, 883 
Pneumatic Convever — M. J. 

Foyer ." 652,960 



Air-Hoist— G. F. Steedman 652,983 

Switch, Pneumatic Carrier — Tai- 

sey 653,044 

Hydraulic Air Compressor— D. 

Kirkman 653,094 

Air Compressor — Bowdser & Sher- 
man 654,511 

Pneumatic Despatch Tube — W. 

Townsend 654,690 

Pneumatic Water-Elevator — 

Shauffleberger 654,764 

Air Purifier— R. H. Thomas 655,285 

Air Power— A. M. Becker 655,541 

Air Brake, Automobile— Ham- 
mond 655,654 

Air-Pipe Coupling — J. W. Spur- 
lock 655,997 

Hydraulic Compressor — Van 

Brocklin 656,147 

Air Brake— F. L. Clark 656,516 

Water-Raising Apparatus— Pe- 

termann 656,572 

Air or Gas Engine — R. H. 

Little 656,823 

Air Compressor — E. Hum 657,025 

Pneumatic Tube Carrier — Batch - 

eller 657,076 

Pneumatic Tube Carrier— Batch- 

eller 657,077 

Pneumatic Tube Carrier — Batch- 

eller - 657,079 

Pneumatic Despatch Tube — Cow- 
ley ....657,090 

Pneumatic Despatch Tube — Cow- 
ley 657,091 

Pneumatic Despatch Tube — Cow- 
ley 657,092 

Pneumatic Gun— E. M. Gold- 
smith 657,344 

Pneumatic Riveter — H.H.Prange. 657,449 

Air Brake— J. J. Nef 657,669 

Air-Actuated Pump— Bartell 657,753 

Compressed - Air Carburator — 

Bouvier 657,755 

Air Compressor— Emile Gobbe. ..657,868 
Pneumatic Despatch Tube — 

Pearsall 657,886 

Reheater— T. A. Edison 657,922 

Pneumatic Despatch — Bavier & 

Hawkes 658,102 

Pneumatic Despatch— Bavier & 

Hawkes 658,103 

Pneumatic Steering — C. Janczar- 

ski 658,265 

Liquid Air— O. P. Ostergren 658,322 

Pneumatic Hammer — E. A. For- 

dyce 658,542 

Li quid- Air Lift— J. Clayton 658,941 

Pneumatic Organ— M. Clark. .. .659,210 

Air Ship— C. Stanley 659,264 

Hydraulic Air Compressor — Web- 
ber 659,270 

Pneumatic Hammer — C. K. Pick- 
les 659,418 

Liquid-Air Lift— J. Price 659,491 



PATENTS. 



8l 5 



Recording Air Pyrometer — Bris- 
tol 659,616 

Pneumatic Type-Writer — M. So- 

blik 659,703 

Air Extractor — Ellingwood 659,730 

Pneumatic Cotton-Picker — Me- 

vers 659,752 

Air Pump and Compressor — G. 

Sipp 659,832 

Air Rifle— W. J. Burrow 660,070 

Pneumatic Stacker — Hixson & 

Tarrant 660,159 

Air Compressor— J. Keith 660,253 

Air Mattress— A. H. Sawtell 660,466 

Air Brake— J. E. Normand 660,650 

Pneumatic Tool — 11. J. Kimman.660,705 
Compound Compressor— T. Grant660,793 
Pneumatic Tool— H. G. Kotten. .660,857 
Air-Gas Apparatus— C. W. Miller. 660, 916 

Air-Lift Pump— T. Butler 660,946 

Pneumatic Hammer — Jones & 

Pierce ..660,961 

Air Cooler— J. T. Nicholson 660,997 

Air Brake — J. R. Richardson. . . .661,075 

Air Brake— J. Shourek 661,111 

Ammonia Compressor— Ludlow . .661,184 
Air-Brake Valve — Krimmelbein. .661,474 

Air Brake— D. Beemer 661,572 

Air-Brake Release Valve— Cor- 

bett 661,574 

Air Brake— W. K. Omick 661,584 

Air-Lift Pump— C. Shaw 661,624 

Air Brake— J. J. Nef 661, 702 

Air Propeller— Newmarker 661,724 

Air-Lift Pump— C. Shaw 661,623 

Pneumatic Hammer — Beckwith. .661,786 

Air Motor— R. A. Gaily 661,860 

Air Furnace— B. A. Brown. 661,950 

Repeating Air Rifle — W. J. Bur- 

" row 662,054 

Petroleum Burner — Charon & 

Manaut 662,055 

Air Vent— A. Roesch 662,093 

Air Brake— W. K. Omick 662,152 

Compressed-Air Engine — M. 

Flood 662,189 

Pneumatic Tire and Shoe — Vree- 

land 662,208 

Water-Ballast Controller— G. B. 

Wilcox 662,330 

Air Conveyer— E. L. McGary .... 662,574 

Pneumatic Carrier— Pearsall 662,601 

Pneumatic Tool — Leineweber 662,675 

Pneumatic Valve-Action — C. M. 

Welte 662,705 

Pneumatic Cash Carrier — F. C. 

Cutting 662,771 

Pneumatic Lubricator — Vandre- 

sar & Pilling 662,838 

Hydraulic Air Compressor — 

Starke 662,884 

Pneumatic Hammer — D. S. 

Waugh... 662,993 

Pneumatic Tire— E. Arthur 663,001 

Air-Brake Coupling— B. Vaughn. 663, 110 



Pneumatic Piano- Action — J. W. 

Crooks 663,118 

Pneumatic Straw-Stacker — Con- 
ner 663,150 

Air-Brake Chart— Lofy & Dinger. 663, 236 

Air Compressor— J. Keith 663,500 

Pneumatic Tire— F. H. Mason. . .663,633 
Pneumatic Refrigerator— Cole & 

Cole 663,731 

Air Compressor — N. A. Christen- 

sen 663,862 

Air-Compressor Regulator— Hew- 
lett 664,086 

Pneumatic Track-Sander— J. B. 

Barnes 664,115 

Aerating Liquids— W. Hill 664,150 

Pneumatic Cushion Post — J. W. 

Stoll 664,184 

Air Compressor— II. M. Salyer. ..664,230 
Pneumatic Spring or Cushion — 

S. H. Stubbs 664,444 

Pneumatic Despatch — J. M. Hes- 

tor 664,547 

Unloading Device — de Laval & 

Aborn 664,562 

Unloading Device — de Laval & 

Aborn 664,563 

Pneumatic Riveter — Tynan & 

Mostiller 664,596 

Air for Furnaces — J. Vicars ... . 664, 695 

Air Valve— T. Wheatley 664,699 

Liquid Agitator— R. Conrader. . .664,723 
Pneumatic Tire— A. H. Lewis. . .664,766 

Air Agitator— E. F. Porter 664,776 

Pneumatic Butler— F. A. Mills. .664,816 
Air Fluid-Lift— G. Schmidt 664,824 

1901. 

Pneumatic Tool— C. B. Richards. 665, 033 
Pneumatic Tool— J. S. Stevenson. 665,281 
Pneumatic Oil-Pump — G. W. 

Turner 665,285 

Pneumatic Hammer Casing — 

Chapman .665,391 

Air-Cooling Device— S. B. Waters 

665,392 
Air Compressor— J. G. Lapham..665,448 
Pneumatic Hammer— J. Beche, 

Jr 665,564 

Train-Signalling Apparatus- 
Harris 665,852 

Rotary Air-Pump— J. Aitken. . . .666,588 
Pneumatic Organ Action — Flem- 
ing 666,658 

Air-Pressure Hoist — Christensen . 665, 993 
Air Water-Elevator— H. L. Frost. 666, 659 
Pneumatic Engine— C.K. Pickles. 666, 690 
Liquid- Air Cooler— J. F. Place. . .666.692 
Liquid-Air Cooler— J. F. Place. .666,693 

Pneumatic Carrier— Fordyce 666.747 

Air Hammer— C. H. Johnson. . . .666,757 

Air Motor— H. L. Arnold 666,840 

Pneumatic Trolley— J. B. Linn. .667,133 
Pneumatic Despatch — C. H. Bur- 
ton 667,185 



8i6 



COMPRESSED AIR AND ITS APPLICATIONS. 



Pneumatic Tube - Service— Fars- 

lund 667,209 

Air Pump— G. W. Kellogg 667,224 

Pneumatic Malting Apparatus — 

F. Knuttel 667,229 

Pneumatic Straw-Stacker — Kit- 

tleson 667,322 

Pneumatic Painting Apparatus- 
Redman 667,369 

Pneumatic Arrow — Kratz-Bous- 

sac 667,630 

Pneumatic Straw-Stacker — T. 

• Goodale 667,694 

Pneumatic Hammer — J. K. 

Lencke 667,784 

Pneumatic Hammer— J. Boyer. ..667,863 
Pneumatic Locomotive Sander — 

Neuffer 667,948 

Air Brake— R. B. Benjamin 668,152 

Pneumatic Impact Tool — Oldham 668,354 

Air Ship— A. F. Hubbard 668,375 

Pneumatic Tire— J. Adair 668,398 

Pneumatic Pump— D. L. Holden.668,405 

Air Brake— Christensen 668,613 

Pneumatic Tire— P. S. Griffith. . .668,733 
Compressor-Lubricator — Michalk 669,065 

Pneumatic Drill— J. Boyer 669,069 

Air Compressor— F. J. A. Kinder- 

mann 669,118 

Gas Compressor — W. Knapp. . . .669,140 

Air Valve— R. L. Ambrose 669,316 

Pneumatic Despatch— Pearsall. ..669,485 
Pneumatic Straw-Stacker — An- 
drews 669,500 

Pneumatic Tool— W. II. Soley. ..670,645 
Pneumatic Tool— W. II. Soley. ..670,646 

Air Bellows— T. P. Brown 670,700 

Rock Drill— Warren Wood 670,750 

Air-Gun— F. F. Bennett 670,760 

Air-Ship- O. Olsen 670,807 

Air Compressor— G. B. Petsche.,670,810 
Pneumatic Tire— P. W. Tilling- 

hast , 670,866 

Air Brake— F. Lince 670,901 

Pneumatic Hammer— C. H. Shaw. 669, 599 
Pneumatic Tire— B. Wakeman. ..669,606 
Air Compressor— G. B. Petsche. .669,853 
Tubular Transmission — Bogardus 

669,888 
Pneumatic Transmission — Bogar- 
dus 669,889 

Tubular Despatch— Bogardus. ...669,890 
Tubular Transmission— Bogardus 

669,891 
Tubular Despatch— Bogardus. ...669,892 
Hydraulic Air Compressor — Lin- 
ton 669,995 

Air Compressor— F. H. Merrill. ..670,000 

Air Compressor — C. Garver 670,153 

Air Brake— W. S. Palmer 670,245 

Pneumatic Hub— T. Coad 670,310 

Air Pump— J. B. Hilliard 670,399 

Pneumatic Tire— Tillinghast. . . .670,412 
Air-Brake Check Valve— W. S. 

Morris 670,563 



Air Compressor — G. S. Binckley.671 
Air Brake — A. Gowperthwait . . . .671 
Compressed-Air Pump — R. W. 

Elliott 671 

Pneumatic Actuator— Schwesin- 

ger 671, 

Air-Pump Governor— Stewart. . .671, 
Ventilation, Tunnel— C. S. 

Churchill 671, 

Pneumatic Tire— A. II. Beck 671, 

Air-Lift Pump— J. E. Bacon 671, 

Pneumatic Tire — Bryan-Hay mes. 671, 
Pneumatic Power-Cylinder — 

Lindstrom 671, 

Liquefled-Air Motor— Ostergren.. 671, 

Rock Drill— H. Koch 671, 

Pneumatic Tire— B. Wakeman. ..671, 
Pneumatic Package-Holder — G. 

H. Wall 671, 

Pneumatic Tire— H. L. Warner. .672, 

Rock-Drill— L. T. Sicka 672, 

Rock-Drill— L. T. Sicka 672, 

Air Barke— G. Westinghouse 672, 

Pneumatic-Tire Valve Tool — 

N/oyes 672, 

Portable Pneumatic Drill— Dean . 672, 
Pneumatic Toy— J. L. Maull. . . .672, 
Pneumatic Tool— T. Barrow. . . .672, 
Pneumatic G rain-Carrier — Scliei- 

degger 672, 

Pneumatic Hammer — J. Dunlop..672, 
Pneumatic Straw- Stacker — Con- 
ner 672, 

Pneumatic Malt System— Renner. 672, 
Pneumatic Despatch— R. T. Jen- 

ney ...672, 

Rotary Motor or Pump — West- 
inghouse 672, 

Rotary Pump — G. Westinghouse. 672, 
Pneumatic Spring — W. W. An- 

nable 673, 

Pneumatic Tire — J. Hubbard. . . ;673, 
Pneumatic Shoe-Form — Ruggles 

& Wiesen 673, 

Valved Piston— J. P. Simmons. ..673, 

Liquid-Air Holder — Bobrick 673, 

Rock Drill— W. Wood 673, 

Pressure-Regulator — Bullock. . . .673, 

Air Valve, Radiator — F. Morgan. 673, 
Air Valve— W. H. Duer . . . . . . . .673, 

Riveting-Tools Supporter— Mull .673, 
Riveting-Tools Supporter— Mull. 673, 

Riveting Apparatus— Mull 673, 

Riveting Apparatus — Mull 673, 

Air-Brake Coupling— J. H. Phil- 
lips 673, 

Pneumatic Spring, Vehicle — Hum- 
phries 673, 

Pneumatic Despatch Carrier— 

Pearsall 673, 

Liquid- Air Apparatus — Hatha- 
way 673, 

Compressed-Air Carriage — Conti . 673, 
Combustion Motive-Fluid Gener- 
ator—Arnold 673, 



044 

207 

671,209 

239 
244 

264 

365 

428 
535 

559 
608 

970 



987 
073 



115 

217 
263 

277 



41 ill 
638 



843 

905 

970 
971 

011 
055 

063 
068 
073 
104 
133 
217 
319 
407 
4 OS 
444 
445 

566 

682 

725 

774 

97S 



PATENTS. 



17 



Pneumatic Grain-Loader— J. E. 

Shepard 674,098 

Pneumatic Shuttle for Looms- 
Baker 674,157 

Liquid - Elevating Apparatus — 

Atkins 674,351 

Pneumatic Despatch— M. Ander- 
son 674,373 

Pneumatic Piano-Playing Device 

—Pain 674,426 

Pneumatic Tire— W. Covintree. .674,436 

Seat for Air-Blast Valves— W. 

Fuller 674,460 

Air Brake— A. J. Brislin 674,493 

Air Brake— J. R. Ide 674,734 

Governor, Air Compressor— 

Christensen 674,808 

Direct -Acting Air Pump — 

Wheeler....^ 674,819 

Air Pump for Bicycles— J. Fur- 
bow 674,829 

Rock-Drilling Machine— M. Sinis- 
ter 674,881 

Regulator, Pneumatic Flue — 

Caffey 674,958 

Handle for Pneumatic Tools — 

Kimman 674,971 

Air-Mixer and Regulating Valve 

—Moore 674,976 

Air Brake System— Moyes & 

Moyes..... 674,977 

Channelling Machine— F. E. Beck- 
man 675,082 

Air-Brake Coupling — McDougall 

675,100 

Pneumatic Hoist— Rutherford . . .675,112 

River Bed Excavator— C. H. 

Brown 675,124 

Pneumatic Tire — Palmer & Ber 

rodin 675,164 

Rock-Drilling Machine— L. Dur- 

kee 675,202 

Pressure Regulator— J. Roger. . .675,246 

Valve for Air Brakes— E. G. 

Shortt 675,251 

Rock Drill— W. S. Bovd 675,319 

Air Brake— J. Guinan 675,328 

Pneumatic Stacker— Mickelson . .675,337 

Regulator, Air Compressor— Prell- 

witz 675,340 

Tunnelling Device— MacHarg 675,355 

Action for Musical Instruments — 

Davis 675.468 



Rock Drill— C. T. Litchfield 675,490 

Motor— C. J. Polock 675,497 

Valve, Pneumatic Hoist — Ruther- 
ford 675,528 

Valve-Gear, Gas Engine — G. An- 
derson 675,581 

Pneumatic Bench-Lift — Doebler 

& Cooper 675,652 

Air Brush— C. Phillips 675,840 

Power Transmitter— A. Benson. . 675,849 

Air Brake— C. A. Ball. . , 675,870 

Portable Pneumatic Riveter— Car- 
lisle 675,880 

Pneumatic Door-Check- 1 — Pere- 
grine 675,903 

Gas and Air Heater for Burners— 

Seifert 675,981 

Stop-Valve for Pneumatic Tires 

— L. Way 675,990 

Separator for Hydraulic Com- 
pressor—Webber 676,016 

Air Brake— Wisner & Ely 676,019 

Air Separator— C. H. Lane .676,041 

Pneumatic Tool— J. J. Tynan. . ..676,055 
Compressing or Exhausting Fluids 

— Reavell 676,080 

Compressed-Air Sprayer — F. Rip- 
ley 676,204 

Hydraulic Air Compressor — 

Mitchell 676,266 

Spring Air-Gun— A. Shoenhut. ..676,279 
Pneumatic Sheet-Feeding Appa- 
ratus—Weiss et al 676,291 

Air Compressor and Explosive 

Motor— Biasse 676,349 

Pneumatic Tire— M. A. Heath. . .676,395 
Air Brake— Mallinckrooz & Sau- 

vage 676,398 

Valve for Pneumatic Tires — 

Spencer 676,400 

Air Compressor — Textorius 676,401 

Pneumatic Straw - Stacker — 

Wright 676,483 

Air Brake— W. H. Sauvage 676,850 

Air Brake— W. H. Sauvage 676,851 

Air Brake— W. H. Sauvage 676,852 

Pneumatic Railway Brake— Brug- 

geman '. ■, 676,871 

Hoist— W. F. Barrett 676,931 

Caisson— W. H. McFadden 676,993 

Rotating Pump or Compressor- 
Dow 677,122 

Pneumatic Tire— Tillinghast 677,290 



I NDEX. 



Air absorbed by water, 32 

absolute temperature and its zero, 

125 
brake, 598-608 

compressor, 287 
blast, 629 

painting, 647-652 
bottle, 310 
brush, 616 
compressors, 271-290 

Clayton, 317-324 

Curtiss, 354-360 

American Steam Pump Co., 380 

E. P. Allis Co., 350 

De Auria, 383 

electric, 319, 385 

Guild & Garrison, 325-327 

gasoline, 404-407 

Ingersoll - Sergeant Drill Co., 
293-307 

four stage, 304-307 

kerosene, 407 

Knowles, 328-335 

McKiernon, 352 

Merrill, 353 

N. Y. Air Compressor Co., 361- 
365 

Nordberg, 391-403 

Norwalk, 339-349 

Rand Drill Co., 369-379 

Pliila. Engineering Works, 382 

Sedgwick-Fisher, 391 

Stillwell-Bierce&S.-V. Co., 386 

St. Louis Steam Engine Co., 381 

Laicllaw D. G. Co., 311-316 

submarine, 625 
compression, low pressure, 107 

isothermal, 116 

two stage, 178-181 
compressor governors, 320, 324, 349 

work, 167 
drills, 479-496 

density and dry, in water, 31, 32 
drying processes, 70 
and vapor (Table), 34, 35 
and gasoline braziers, 109 
in motion and force, 43-45 
flow in pipes, 216-222 

into vacuum, 87 
for rock drills, 417-436 
flow from orifices, 91 



Air, gold separator, 110 

guns, 696-699 

lock system, 668 

liquid, 787 

lift pump, 712-729 

loses by transmission, 222 
efficiency, 716 
hammers, 447-471 

nozzle, type, 92 

physical properties, 31-40 

plant in Paris, 243 

power transmission, 213 

pressure cards, Corliss engine, 253, 
254 
pump, 728 

pressures below atmospheric press- 
ure, 51-69 

pyrometer, 559 

signal equipment, 605 

signals, 593-595 

storage, 308-311 

specific heat, 123 

vacuum pumps, 51-53 

to run hoisting engines, pumps and 
motors, 260-266 

transmission tables, 219-221 

valves, 295, 357, 372 
Action of duplex air compressor, 285 
Actual work of the compressor, 165 
Adiabatic card of work, 169 

compression and expansion, 135 
Aeration of water, 739 
Aging of liquors, 744 
Allen dense air machine, 758 
Anemometers, 45-47 
Atmosphere, height, 32, 33 
Ammunition lift, 701 
Automatic switch, 726 
Automobile reheater, 233 
Auxiliary valve, 418 



Bado-er rock drill, 431 

Balfand nozzle, 108 

Baggage handler, 595 

Barometer, pressures, water boils, 38 

Bar channelling, 423 

Basket-making, 615 

Bell ringer. 609 

Belt compressors, 296, 299, 317, 322, 355 

Bessemer converter, 663 



INDEX. 



819 



Blowers, types, 107 
Blast, air, 629 

sand, 630 

furnace, 663 
Blasting coal, 667 
Blowing engines, 350, 351 
Boyer drill, "483-486 

hammer, 456, 457 
Brazing apparatus, 109 



Caisson disease, 777 

sinking, 663-675 
Card of compressor and motor work, 244 
of slide valve air engine, 245 
of two-stage compressor, 179 
of three-stage compression, 186 
of four-stage compression, 189 
Cards of Corliss air engine, 253, 254 
Caloric, 122 
Carriers, tube, 681 
Carpet-cleaning, 654-659 
Caloric engine, 234-239 
Coal cutters, 423-425 
Chicago rock drill, 427 

pneumatic drill, 490 
Clearance table for motors, 201 
Coefficients of air velocity, 93 
Compound air compressors, 290, 340, 
343, 347, 353, 359, 373 

lift, 721 
Compressed air hygiene, 775 

in blast furnace, 663 

for blowing glass, 110 

for blasting coal, 667 

for hoisting engines, 260 

in mining, 417 

cars, 574-585 

haulage, 587 

on railways, 573-586 

in rolling-mill, 665 

in ship-building, 492-496 

storage, 309, 310 

pumps, 730-737 

refrigeration, 748 

indicator card, 155 

tables, 144-151 

for raising water, 711-737 

in warfare, 695 
Compressor efficiencies at altitudes, 258 
Combustion in cylinders, 408 
Condensation by compression and cool- 
ing, 39 
Condenser air pumps, 56-58 
Contents of cylinders, cubic feet, 259 
Cooling water by air expansion, 770 
Corliss type, 303, 362, 374, 382, 392-398 
Cold rooms, 764 
Cost of compressing air, 587 

of reheating air, 232 
Cross compound air compressors, 301, 

314, 315, 373 
Curves, adiabatic, 140, 141 
Cyanide and air gold process, 742 



D 

Darlington hydraulic air compressor, 282 
Dense air refrigeration, 760 
Dewar apparatus, 797 
Diagram, isothermal compression and 
expansion, 116 

adiabatic compression and expan- 
sion, 137 

combination curves, 139 

of air expansion, 765 

of three-stage compression, 187 

of four-stage compression, 188 
Direct-acting compressors, 330, 353, 380 

pressure pumping, 724-726 
Diving armor, 623 
Drills, air, 479-495, 521 
Driven-well system, 734 
Dry-placer mining, 110 
Drying in vacuo, "64-72 
Dumping cars, 597 
Dubois & Francois compressor, 282 
Duplex air lift, 721-725 

compressor, action, 285, 289 

compressors, 300, 303, 312, 316, 320, 
333-335, 350, 351, 362-364, 371 

Pelton wheel compressor, 298 

vertical belt compressors, 355-358 
Dusting by compressed air, 653-656 
Dust filter, 654 
Dynamo run by windmill, 105 



Edison reheater, 225 
Efficiency of air lift, 716 

of Grass Valley plant, 251, 252 

of motors, 246, 247 

of compressors, high altitudes, 257 
Electric lighting by wind power, 105 

air compressor, 319 

meter, 563 
Endless chain in air pumping, 736 
Engines, free air to run, 260 
Energy in tube transmission, 684 
English tube system, 682 
Engraving, air, 644 
Ecpaations of compression, 144 
Ericsson hot-air engine, 235, 236 
Expansion, card computation, 200 
of work, 197 

formulas, 198, 199 

of compressed air and work of mo- 
tor, 197-209 

mean pressure, 1 99 

temperatures, 198 

work and formulas, 206-208 
Explosions in cjdinders. 408 
Evaporation by air (Tables), 47, 48 
Evaporators, J. Oats & Son, 83, 84 

Lillie, 81, 82 

Yaryan, 77-79 



Files, sharpening, 645 
Filter hood, 654 



820 



First law of thermodynamics, 122 
Flow of compressed air in pipes, 216-222 
Food products, drying, 64-69 
Foot-pound work of compression, 170-171 
of multiple compression, 191, 
192 
Fog signals, 617 
Formulas for air tables, 218 

expansion and work, 198, 199 
air velocity, 93 
isothermal, 118 

for ratios of expansion, 203, 204 
"thermodynamic, 128, 129, 139, 142, 

143, 170, 171, 172 
for multiple compression, 191-193 
work of expansion, 206-208 
for air flow in pipes, 216, 217 
Four-stage air compression, 187-193 

compressors, 302, 304, 306, 307 
Free air to run drills, 426 

to run engines, pumps and mo- 
tors, 260, 266 
Friction loss of air pressure in pipes, 222 
Frizell hydraulic air compressor, 272 

G 

Gasoline and air torch light, 108 

soldering and brazing, 109 
air compressors, 404-407 
Gas engine air compressor, 361 
Gay Lussac's law, 121 
Gold mining by air pressure, 110 
Governors, air pressure, 321, 324, 349, 396 
Grain ventilation by air pressure, 110 
Graydon gun, 699 

H 

Haesler pneumatic drill, 480 

Hammers, air, 447, 499, 507, 508, 511 

Hand air compressors, 390 

Hargrave kite, 100 

High pressure compression types, 290, 

304, 377-379 
Hartford air compressor, 280 
Heat a mechanical quantity, 122 
Hoisting engines, air required, 260 
Hoists, air, 533-553 

Horse power for compressing air, 181, 192 
Hold -on, 462, 511 
Hot-air engines, 234-239 
Hydraulic air compressors, 271-282 

motor, 248,252 
plant, Grass Valley, Cal., 248-252 

Iron Mountain, Mich., 252-254 
Hygiene of compressed air, 775 



Ice machine, Gorrie, 752 
Impact or force of percussion, 437 
Imperial type, compressor, 375 
Indicator card, the, 155-159 

steam and air, 160 
Indicator cards, computation, 200 

hot air engine, 239 



Indicator cards, multiple compression, 

186, 189 
Ignition in cylinders and receivers, 410 
Ingersoll- Sergeant rock drills, 419-423 

coal cutter, 424, 425 
Injector, air, 630 
Intercooling and intercoolers, 182, 185, 

340, 403, 413 
Interlocking signals, 594 
Isothermal card of work, 167 
compression of air, 115 
diagram, 116 

J 

Jacks, air, 550, 551 
Jet compressor, 109 
condensers, 57, 58 

K 

Kalsomining by air jet, 647 
Kerosene air compressor, 407 

in air cylinder, 409 
Kites and their work, 99-102 

L 
Leyner rock drill, 432 
Lift, store service, 686 
Linde liquid-air apparatus, 793, 794 
Liquid air, 787-802 
Liquid-air plant, 798 
Little Giant drills, 481, 482 
hammers, 452-454 
Locomotive bell ringer, 609 
Locomotives, 589-592 

Baldwin type, 589 

Porter type, 592 
Log flipper, 615 

nigger, 116 
Losses in air pressure by transmission, 222 

M 

Mean pressure card, 159 
table, 149 

Mechanical efficiencies, 190 
equivalents, 123, 124 

Mekarski reheater, 231 

Mercurial air pump, 54 

Meter measurement, compressed air, 266 
268 

Moisture in air (Tables), 35, 36 

Motor, compressed air and work, 197 
efficiencies; Paris, 246, 247 
work; Kennedy report, 244 

Motors, air required to run, 265 

McKiernan rock drill, 429 

Mountain pressures ; water boils, 38 

Moulding machine, 516 

Monitor Terror, air work, 700 

Multiple-stage air lift, 721, 722 

Multi-stage air compression, 177-181 

N 
Nozzle, air type, 92 
dusting,* 653, 654 
paint spray, 648 



INDEX. 



82 1 



O 

Orifices, flow of air through, 91 



Pelton wheel air compressors, 248, 2£ 

341, 342 
Piston air drills, 505-510 

inlet and valve, 295 
Petroleum burner, 647 
Phoenix drill, 488 
Power of air, 437 

plant; Paris, 214 
Pohle air lift, 712, 713 
Point of stroke (Table;, 149 
Pneumatic tools, 447-551 

drills, 479-495, 521 

guns, 696-699 

hammers, 447-499, 507 

hoists, 533-553 

jacks, 550, 551 

nozzles, 653, 654 

punch, 555-557 

painting, 647-652 

saw, 551 

sheep shearing, 613 

stay-bolt cutters, 549 

telegraph, 598 

tools in ship building, 466-471 
construction, 472-478 

postal tube service, 676 

welding machine, 517 
Pressure of air at sea level, 124 

and heat diagram, 139 

of the wind (Table), 44 
Preservation of wood by vacuum, 68 
Pumping by wind power, 104 
Pumps, air required to run, 261, 264 
Purifying water by air, 740 
Pyrometry, 555-569 

Q 

Q. and C. hammers, 450, 451, 499 



Railway gate, 596 
Eaising water, 711-737 
Rammers, sand, 512, 513 
Rand rock drills, 434-436 

reheater, 229, 230 
Ratio of expansion, 126 
Ratios of compression (Table), 149 
Reducing valve, 583 
Refrigeration, 747-770 
Regulators, air pressure, 349, 396 
Reheating of air and its work, 225-233 
Rider hot-air engine, 237, 239 
Riveter, stationary, 505 

yoke, 472, 475. 503, 504 
Rock drills, 417-436 
Rock-drill reheater, 226 
Rolling-mill, 665 
Rotary drill, 488 



S 

Salt-making in vacuo, 72-75 
Sand brush, 515 

sifter, 515 

blast, 630-641 

blast cleaning, 646 
Sculpture and stone cutting, 463, 464 
Sergeant reheater, 227, 228 
Sawmill, compressed air in, 615 
Sewage lifting, 737 
Simple reheater, 225 
Sheep shearing, 613 
Signals, air, 593-595 
Siren or fog-horn, 618 
Siphon, 85 

pressure gauge, 47 
Stage compression, 178, 193 
two stage, 178, 181 
three stage, 186, 187 
four stage, 187, 193 
Stay-bolt cutters, 549 
Steering apparatus, 706 
Steam and air card, 160 
Store service, tube, 687 
Stone hammers, 502 
Straight-line air compressor, 287 
Submarine exploration, 621-626 
Sunken vessels, raising, 619, 620 



Table I. Air absorbed by water, 32 

II. Air and vapor, volumes and 
weight, 35 

III. Moisture in air at various press- 
ures, 36 

IV. Weight of vapor per cubic foot, 
37 

V. Height of barometer-boiling tem- 
perature, 38 

VI. Water condensed from com- 
pressed air, 40 

VII. Wind velocity and pressure, 44 

VIII. Evaporation of water by air, 
48 

IX. Evaporation in vacuo, 59 

X. Velocity of air from orifices, 91 
XL Velocity and air coefficients, 94 

XII. Flow in cubic feet from orifices, 
94, 95 

XIII. Windmill power, 104 

XIV. Specific heat of air, 124 

XV. Volume, pressure, and density. 
Air, 129 

XVI. Pressures, temperatures, and 
volumes, 145 

XVII. Gauge pressures, ratios, point 
of stroke," 149 

XVIII. Mean pressure in cylinder 
and delivery, 166 

XIX. Foot-pound work of com- 
pression, 171 

XX Power lost in compression, 180 
XXI. Horse power; multi-stage 
compression, 192 



822 



INDEX. 



Table XXII. Excess of cut-off for clear- 
ance, 201 

XXIII. Eatios of pressures and tem- 
perature, 202 

XXIV. Mean and terminal pressures 
in motor, 205 

XXV. Pipe areas and coefficients, 
217 

XXVI. Gauge pressures, weight, 
Vw^218 

XXVII. Air transmission, 45-pounds 
gauge, 219 

XXVIII. Air transmission, 60- 
pounds gauge, 220 

XXIX. Air transmission, 75-pounds 
gauge, 220 

XXX. Air transmission, 90-pounds 
gauge, 221 

XXXI. Air transmission, 105-pounds 
gauge, 221 

XXXII. Loss in air pressure in 
pipes, 222 

XXXIII. Compressor efficiencies at 
altitudes, 258 

XXXIV. Contents of cylinders, 259 

XXXV. Free air required for hoist- 
ing engines, 260 

XXXVI. Free air required for 
pumps and motors, 261 

XXXVII. Free air required for 
pomps, "Weber," 262 

XXXTIII. Free air required for 
pumping water, "Halsey," 264 

XXXIX. Free air required per I. 
H. P. "Weber," 265 

XL. Free air required for rock drills 
"I. S. D. Co." 426 

XLI. Free air required for Rand 
rock drills, 435 

XLII. Factors for drills at elevation, 
436 
Tandem Corliss compressor, 289 
Tappet valve, 418 

Taylor hydraulic air compressor, 273, 279 
Telegraph, air, 598 
Temperature, boiling, at altitudes, 38 

diagram, 139 

in hot-air engine, 237 
Terminal air pressure, 198 

valves, 689 
Terror, monitor, 700-707 
Thermodynamics, 121 
Thermal unit, 122 
Three-stage air compression, 186, 187 

compressors, 323, 345, 346, 400 
Tilden hammer, 458 
Transmission of air power, 213 

air tables, 219-221 

long distance, 220 
Triple valve, 599-601 
Tripler liquid air apparatus, 796 
Trolley car air brake, 607 
Trompe, 271 
Tube transmission, 675-686 



Tube well air lift, 723- 

Two-stage air compression, 178-181 

lift pump, 726 
Types of air compressors, 283 

U 

Unloading devices, 295, 297, 370, 39: 
Utility of a vacuum, 64-84 



Vacuum and its work, 51-84 

excavator, 85 

flow of air into, 87 

process for salt, 72 

pumps, 52-69 
Valve, reducing, 583 
Valves, air brake. 599-604 

compressor, 327, 357, 358, 359 
Velocity and pressure, wind, 44 

of the wind and force, 104 
Venturi nozzle, 92 

vacuum pump, 53 
Vertical air compressors, 329, 355, 356, 
365, 381 

valve cylinder, 295 
Volume of expansion for any tempera- 
ture, 129, 130 
Vulcanizing wood, 743 

W 

Wall or post compressors, 317, 328 
Water aeration, 739 

condensed from compressed air, 40 

works, 717 
Weight of air, 124, 130 
Welding machine, 517 
Windmill and its work, 102 

for electric lighting, 105 
Wind power, 99 

velocity and force, 43, 44 
Whitlaw drill, 485, 491 
Whitewashing by air, 647 
Whistles, air, 616 
Wood vulcanizing, 743 
Work, adiabatic diagram, 169 

isothermal diagram, 167 

of expansion, 206-208 

foot pounds of compression, 168-172 

foot pound, multi-compression, 191— 
193 

of the sand blast, 633 

of reheating, 225, 233 

of the compressor, 165, 167 



Yacht and launch whistles, 616 

Yaryan evaporator, 77 

Yoke riveters, 472, 474, 503, 504 



Zalinski gun, 696 

Zero diagram of absolute temperature, 
126 




Quarry- 
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COAL 
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